Despite his close cooperation with Constantinos Karamanlis, during the exile period in Paris, he was not included in the combinations of the New Republic party, in the 1974 elections, thus to stand as an independent parliamentary candidate in the prefecture of Chania. In this election, despite the large number of votes received, he was not elected.
In the intervening period, between 1974 up until the 1977 parliamentary elections, Konstantinos Mitsotakis took steps to reconstitute the Centre Union. He suggested a conference convergence with all candidates of the Centre Union in the elections of 1964 and 1974, for the election of a new leadership and the determination of its political action. His efforts, however, crossed fruitless and so, on September 6th, 1977 he founded the Liberal Party. In a statement of fact, he delivered the same day, justified the reasons that led him to undertake this initiative. In particular, during that declaration Konstantinos Mitsotakis mentioned:
"My repeated proposals for the unification of the forces of the old 'Center Union, aiming in the repatriation of voters who moved in 1974 to the "NEW DEMOCRACY" and the creation of a successor governmental schema remained unanswered, thus meaning denial. So I proceed to the next phase of my announcements, last May, founding a new political movement, named the "NEOLIBERALS PARTY". The respective statement was tabled today in the Supreme Court, as required by law. It is about the reconstitution of the "Liberals Party", adapted to the needs of the time. With the slogan more freedom, more equality, more justice, more democracy, the "NEOLIBERALS PARTY" sets as a long-term goal the renewal and modernization of the country's political, economic and social life and the establishment of true democracy. For the realization of this objective, the "NEOLIBERALS PARTY" is first intended to be an alternative to the current political impasse that the deficiency of the governing party and the inability of the opposition led the country to. The immediate objective of the "NEOLIBERALS PARTY" is to fill the political vacuum, existing today because of the deterioration of the government and the opposition. For this reason, the "NEOLIBERALS PARTY" is addressed to all Greeks, but especially to the 55% of "NEW DEMOCRACY" and the 20% of EDIK (Democratic Center Union). The alternative to these two partisan formations, which failed so far to persuade, that they are able to govern the place and to guarantee the continuity and stability of democracy. We will become it. Within a short time will be announced the collective bodies of the party and their composition and the provisional statute of operation, being prepared already by an informal committee. In parallel, preparatory work for the establishment of Prefectural Committees has been done and soon, the announcement of their operations will begin, while immediately after the formation of the interim collective bodies, a committee will be appointed to prepare the Party Pre-Congress, which we hope to meet within the first months of next year, and if the 4-years term will be exhausted, we will try to organize the Party Congress before the elections of Autumn 1978. The Party's political program will be processed by special committees, to be determined by the interim collective bodies and notified partially and by sector. Finally, firm decision of the "NEOLIBERALS PARTY" is to participate in the next elections independently and with combinations throughout Greece ".
The "NEOLIBERALS PARTY" led by Konstantinos Mitsotakis, was involved in the early elections held in November 1997 succeeding by a rate of 1.09% and winning two parliamentary seats. Other than him, who, as party head was elected, a seat was won by Pavlos Vardinoyannis. In May 1978, Constantine Karamanlis announced the enlargement towards the Center policy of the New Democracy party. Konstantinos Mitsotakis joined the New Democracy Party and undertook the Ministry of Coordination during the critical three years before Greece joined the European Economic Community. In George Rallis's government, formed in May 1980, he took over the Foreign Ministry until the elections of 1981. As Minister of Foreign Affairs, he began a dialogue with Turkey; he visited Ankara and reignited Greek-Turkish relations. Additionally, he created good neighborly and cooperative relations with the Balkan countries and also developed the Greek relations with the Arab world, cooperation not only in the fields of politics, but also in trade, economy, technical and education. Alongside, he succeeded in the reintegration of Greece with the military wing of NATO, from which the country had left in 1974 because of the passive attitude of the alliance against the Turkish invasion of Cyprus. From October 1981 until August 1984, he was the parliamentary spokesman of the New Democracy party.
Following the resignation statement of Evangelos Averof, from the leadership of New Democracy (August 29, 1984 till August 31, 1984), Konstantinos Mitsotakis announced his candidacy for the leadership of New Democracy. His candidacy proposal, was signed by Members Sotiris Kouvelas, George Sourlas, Vassilis Mantzoros, Athanasios Xarchas and Anna Synodinos. In a related statement of his, following the submission of his application, Konstantinos Mitsotakis said:
"I have already stated and I consider it my duty to repeat again that, I will accept whatever the outcome of the vote will be on tomorrow's voting. True fighter of our great liberal faction, I will continue to fight in any rampart the party will specify. I am certain that tomorrow our party begins a new dash for the final victory".
On September 1st, 1984 he was elected, by New Democracy's Parliamentary Group, party president by a large majority. Specifically, Konstantinos Mitsotakis received 70 votes against 41 votes received by the other leadership contender, Kostis Stephanopoulos. Immediately after the announcement of the outcome of the internal party process, Konstantinos Mitsotakis spoke as the new party leader, to New Democracy's Parliamentary Group, giving his political position and outlining the oppositional strategy towards PASOK and Andreas Papandreou. In particular, in his speech he said: "With deepest emotions I express my heartfelt gratitude to the Parliamentary Group, as with its free and responsible vote elected me chairman of New Democracy. I feel the great honor and the heavy debt. It is natural for one to reconsider his responsibilities on the top of a party that he founded and directed, one of the most powerful political figures in Europe, Constantine Karamanlis, who was brightened by George Rallis's democratic sensitivity and wisdom and lifted again to a great country political force, his tireless creative activity, high political ethos and personal bravery of Evangelos Averof. It falls up to me to assure my colleagues and the Greek people that I will consume all my strength in the service of the party and its ideas and that we, all together, united and rejuvenated, will soon lead our great party to victory and to power".
Then he described the main tasks of the MPs and oarty members for the new period within the political actions of New Democracy stressing: "... First, from this moment on, having completed the succession process and the will of the Group was reflected, shall end the reasonableness and democratically legitimate opinion differences referred to personal preferences. From this moment on we are still inextricably brothered, the compact 111 having fulfilled the task democratically. (...) Second, with the valuable cooperation of my dear friend, Costis Stephanopoulos, we will solidify the unity of this party, on which its future depends. It will be protected in all ways, the fundamental right of criticism and inner-party dialogue. (...)Third, we will strive in all ways for mild political climate, prevent acidity and political moderation. The powerful do not resort to acidity. It is enough for them, the steady, unyielding militancy and decent candor. (...) Fourth, our main goal is, as the resigning New Democracy leader proclaimed, the reconciliation of the Greek people, who is threatened to be divided by the bigotry and partisan passion at moments critical for Hellenism. Fifth, our ambition is to establish a new public ethos, where communication with the people will be immediate, regular, and honest. Neither unfulfilled promises, nor misleading statements, or populist programs (...) Sixth, our goal is a modern party. We will move decisively to the renewal, not just meaning new age persons and persons not tested until now, with new ideas and innovative imagination. And the renewal must necessarily be combined with meritocracy, which especially under the current circumstances is a national need. Without adherence to doctrines, we will prove that our party can balance the past with the future, tradition with progress, freedom with justice, realism with imagination ..."
Commenting on the political situation of the country, Konstantinos Mitsotakis said: "...Our country, ladies and gentlemen, passes one of the most critical phases of its modern history. The lack of seriousness and unilateral external orientations of the governing party threaten our shoulders and our traditional and critical friendships during moments of supreme national hazards. The Greek economy is ravaged by dogmatism, the amateurism and demagogy, so that there is no hope for recovery, while European and US economies entered a phase of new development and the working classes, SMEs and the disadvantaged suffer, while private initiative is strangled by party passion. Internally, gradually occurs, albeit with retractions and misleading complacency, the slipping of the regime to a one party system. Parliamentarism has been falsified, the cabinet is in ruins, the political responsibility has deteriorated with the extra-parliamentary ministry assignings, the abolition of the cross has injured popular sovereignty, the administration has been party overtaken and dismantled, information objectivity has disappeared, the free syndicalism turned into state syndicalism, power personified, the economy is collectivist and a barrier rises between the people and the government ... "