Stepping up his offensive against Prime Minister Manmohan Singh [Images], former external affairs minister K Natwar Singh said on Wednesday that he was a 'weak' prime minister who was unable to stand by his colleagues in difficulty.

"It gives me no pleasure to say that he is a weak PM, unable to stand by his colleagues," he told Karan Thapar in an interview on CNN-IBN, a day after his suspension from the Congress for misusing his position to get Iraqi oil contracts for persons close to him.

"I have worked with him (Dr Singh) for 40 years and he knew nothing of foreign affairs. Now, when I am in difficulty he does not have the courage or camaraderie to say something in my favour," he said.

Without naming anyone, Natwar Singh, alleged that two ministers in the present government had hatched a conspiracy against him. Asked whether he was pointing an accusing finger at Union Ministers P Chidambaram and Kapil Sibal, he said, "It is for you to draw your own conclusion."

Natwar Singh also alleged that the two minsters had selected lawyers having prejudice against him to assist the Pathak Inquiry Authority, which probed the Iraqi oil scam and indicted him and his son Jagat for misusing their positions to get oil contracts for persons close to them.