Malaysian Prime Minister Mahathir Mohamad took the oath with other lawmakers in Parliament today, making the 93-year-old the world’s oldest leader – and one that has beaten the odds with a landslide win in the Malaysian elections and promises for a brighter future that simultaneously deals justice but leaves the past where it belongs.

Al Jazeera spoke to Mahathir Mohamad about questionable alliances with a man he put behind bars, Anwar Ibrahim, and his vision for Malaysia’s economy.

Al Jazeera: Najib Razak, your predecessor, called you “Malaysia’s number one actor” after your alliance with Anwar Ibrahim and the rapprochement that you made with him. Now, is that rapprochement and that reemergence of a coalition a genuine attempt to rectify mistakes and maybe unify Malaysia once again or is it, as former Prime Minister Najib claims, an act to reinvent yourself and maybe lead you back to power?

PM Mahathir Mohamad: Anwar was head of one of the major parties in the opposition. If we are going to overthrow Najib, all the parties in opposition must form a coalition. Going on their own, they will never be able to defeat him.

So, it was decided that we form a coalition, and whatever may have happened in the past, that is not as important as the attempt to overthrow Najib. What Najib has done is terrible for the country.

So, Anwar and myself, and many others who in the past accused me of all kinds of wrongdoings, we decided that the past is the past. Now, we have to come together, because the overthrowing of Najib is far more important than our previous quarrels.

Al Jazeera: What was it that was so bad that Najib did, as far as you were concerned? What were the main threats to Malaysia?

Mahathir: Number one, of course, he was involved in a lot of scandals, including the accusation of his stealing money from the government, a not small amount. Billions of ringgit. Also, there was this evidence brought out by the American Department of Justice.

We cannot ignore all these things and say, “This did not happen.” The whole world believes that this happened. So, we must make sure that if there is any basis for the accusation that it must go to a court of law.

Al Jazeera: How did the system allow for the prime minister to interfere to the point where he was able to fire the lead investigator? Now, you are prime minister and the same system is still there; What checks and balances are there to prevent you from doing the same?

Mahathir: I could do the same thing, but I didn’t do it. You see, I was 22 years as prime minister. There was no accusation of stealing money against me. All the other accusations were just political accusations with no proof.

In the case of Najib today, we have enough evidence, and the rule of law must be applied.

Al Jazeera: You promised, as part of your campaign, that you would secure a pardon for Anwar if elected, and you’ve done that. But you’ve also promised to hand him the reins within two years. Why two years? Also, what guarantees are there that you won’t change your mind?

Mahathir: Because I am old … We need to form a coalition in order to defeat Najib. The coalition must include Anwar’s party. The condition for Anwar to join the coalition is that he will be the next prime minister after me.

Al Jazeera: One of the criticisms that you faced when you were prime minister the first time was that you curbed freedoms through the Internal Security Act or had opponents jailed, like Anwar. Are you looking to use the same strongman approach this time, or is your approach maybe more of a unifying, healing phase that Malaysia needs to go through?

Mahathir: I have to go according to the manifesto set up by the coalition. I am not free to do anything I like because I am bound to carry on what the coalition has decided, and the coalition has decided that we will go back to democracy.

We will go back to the rule of law. So today, I cannot on my own arrest anybody. During my time, I didn’t make use of my power to arrest people at random. There must be a cause.

Al Jazeera: You’re credited with transforming Malaysia’s economy, making it one of Asia’s so-called “tiger economies”. Things have slowed down in the last few years because of the corruption, but also other issues. What are your plans to revive Malaysia’s economy?

Mahathir: We have a lot of plans for resuscitating Malaysia’s economy. First of all, we have to get rid of this debt that we carry, a huge debt amounting to more than one trillion Malaysian ringgit.

We have to reduce this debt so that the country is not settled with having to pay interest and principal on this debt, which will prevent us from having the money for development of the country.

Al Jazeera: You are the eldest head of state in the world. You have witnessed many world events. What are the highlights of your career, that you look back on and maybe your proudest moments? And is there one thing you regret most?

Mahathir: Being the leader applies skills or knowledge to the development of the country. I did what I was able to do and I was satisfied that I have given my best for my country. That’s all.

Now, I am again in a position to take corrective action, and if I don’t, I think it’ll be very selfish indeed. If I am still able, I will contribute whatever I can towards resuscitating this country, which has the potential to become a developed country, provided the policies of the governments are correct.