KUALA LUMPUR (THE STAR/ASIA NEWS NETWORK) - Malaysian Prime Minister Datuk Seri Najib Razak has blamed the opposition for being behind a fake letter claiming his deputy Ahmad Zahid Hamidi had wrote to him asking him to step down.

Datuk Seri Najib said the fake letter, which went viral on social media, was the work of an opposition "envious" of the "absolute solidarity" seen at the recent Umno general assembly.

"They are envious of the total solidarity within Umno and Barisan Nasional," the Prime Minister said in a statement on Saturday (Dec 10).

"So it's not surprising that they are now spreading rumours in an attempt to undermine my close relationship with the Deputy Prime Minister. Perhaps they are mistaking his character with some former party members, who were driven by personal interest, not the party or national interest," he said.

He urged Umno members to be wary of what he said were dirty tactics used by the opposition.

A picture of the supposed letter by Datuk Seri Dr Ahmad Zahid Hamidi calling for Mr Najib to step down made its rounds on social media over the weekend.

"The opposition is now so desperate and in such disarray that they have been forced to ally themselves with the man who jailed their own leaders," Mr Najib said, in a reference to his former mentor turned critic Tun Dr Mahathir Mohamad.

"I urge all party members to be alert to the dirty tactics used by our enemies," he added.