Datuk Seri Mukhriz Mahathir resigned as Kedah chief minister yesterday, claiming he was forced out after a two-week impasse due to his criticism of Prime Minister Najib Razak.

The son of former prime minister Mahathir Mohamad will be replaced - after just 30 months in his post - by Datuk Seri Ahmad Bashah Md Hanipah, 66, the Kedah Umno deputy chairman.

Mr Ahmad Bashah had led Kedah Umno division leaders in claiming that Mr Mukhriz, 51, had failed to govern well and strengthen the party in the northern state.

Fourteen out of 15 Kedah division leaders withdrew support for the latter's administration on Jan 20.

"To avoid this political crisis... prolonging and affecting the administration of the state to the detriment of the people, I have decided to relinquish the role of Menteri Besar of Kedah effective immediately," Mr Mukhriz said at a press conference in Alor Star, the state capital. He made the announcement after being informed by the royal Kedah Regency Council that he had lost majority support in the state assembly.

Insisting he remains loyal to Umno, he took a parting shot at Datuk Seri Najib, whom he described as "childish", saying "the real reason this action was taken against me was because of the criticism I voiced out". Mr Mukhriz was referring to his statements on state investor 1Malaysia Development Berhad's (1MDB) struggles with debt and the US$681 million (S$972 million) found in Mr Najib's private bank accounts last year.

"Sorry to say that as long as Najib is still there, Umno is at its weakest point right now. Scandal after scandal, I think we can't take it all, it is too much for us. It is really traumatising to all of us. We can't hold our heads high. Now I will have more opportunity to fight on and speak out for the people because this will not shut me up," he said.

Mr Mukhriz also told reporters he was offered a federal deputy minister post but declined it, adding that he would continue to serve as Ayer Hitam assemblyman.

He became Kedah Menteri Besar in 2013 after the Barisan Nasional (BN) coalition wrested the state from the opposition. BN's dominant party Umno controls 19 of the 36 seats in the state legislature, with ally Malaysian Chinese Association holding another two.

His resignation came after an exhaustive series of meetings earlier in the week between the Regency Council, which played a mediating role in resolving the deadlock, and assemblymen from both the ruling BN coalition and the opposition.

The Regency Council met the 21 BN lawmakers on Monday, but it is understood that several assemblymen refused to back the plan to oust Mr Mukhriz.

On Tuesday, before they met the Regency Council, the 15 opposition lawmakers in Kedah called for a confidence vote to be carried out in the state assembly to determine whether Mr Mukhriz should retain his post. The chief of the opposition alliance, Datuk Seri Wan Azizah Wan Ismail, said the opposition was likely to vote in support of Mr Mukhriz.

In a statement yesterday, Mr Najib's office insisted that Mr Mukhriz had to resign because he had lost the support of his Umno state assemblymen, who were concerned that "better preparations were needed to retain Kedah in the 14th general election". It added: "Kedah Umno have demonstrated their support for these principles of party unity and discipline."

Meanwhile, Umno leaders including Tourism and Culture Minister Nazri Abdul Aziz denied that Mr Mukhriz's ouster was linked to Dr Mahathir's criticism of Mr Najib.

"If it was that, he would have been kicked out a long time ago when the father started speaking out about 1MDB and all," he told Malay Mail Online.

Mr Ahmad Bashah will be sworn in as Kedah chief minister this morning.