Kuala Lumpur  - Malaysia's former prime minister Mahathir Mohamad rejoined the ruling party Saturday, one year after he quit following a falling out with his successor.

Mahathir's decision to rejoin the United Malays National Organisation (UMNO) came a day after Najib Razak was sworn in as new prime minister.

Najib took over from Abdullah Ahmad Badawi, who had been Mahathir's chosen successor after he retired in October 2003.

However, less than a year later, Mahathir began slamming Abdullah for cancelling many of the mega-development projects pitched during his 22 years in power.

Mahathir then launched into public criticism of his former protege's rule, and joined a chorus of critics in blaming Abdullah for major losses sustained by the ruling National Front coalition during last year's general elections.

Mahathir had quit in 2008, promising only to return once Abdullah steps down.

Finally, Abdullah caved in to pressure from his critics and resigned Thursday.

"I believe Mahathir's return will provide a strong impetus to UMNO and can help in the rejuvenation" of the party, Najib said Saturday at a ceremony where Mahathir submitted his membership forms.

Mahathir said he was happy to return and urged those who had left along with him to follow suit.

Mahathir said there was now work to be done to rebuild the party's image and regain public confidence in the party and the government.

During the general elections, the Front failed to get a two-thirds majority in parliament and lost an unprecedented five states, the Front's worst-ever results in its 51 years in power.

Late Friday, Najib made his maiden speech as premier by announcing he was freeing 13 people held under a draconian law that allows indefinite detention without trial, and also lifted a ban on two opposition newspapers.

However, the fate of some 30 others who remain detained under the Internal Security Act was unclear. (dpa)