Dumurjola, May 1 : In a stinging attack on Left parties, Prime Minister Manmohan Singh on Friday said their policies are "retrograde" and "lack far-sightedness" and contended that their withdrawal of support to the UPA government last year indirectly helped BJP.

Addressing a public meeting here in Howrah district, Singh accused the Left parties of spreading wrong information on Indo-US nuclear deal and termed their withdrawal of support on the issue as a "mistake".

He said the Left has "committed many mistakes. It withdrew support to UPA government on the nuclear deal which indirectly helped the BJP."

Singh, who was addressing his first election meeting in West Bengal, said "The Left wrongly claimed that we pursued pro-American interest while clinching the N-deal. This is not true ... We signed the agreement to augment country's energy requirements ... and this was informed to countrymen by the UPA government."

Sharing dais with Trinamool Congress chief Mamata Banerjee, the Prime Minister said Left had not changed its thinking with the passage of time. "The CPI(M)'s stand is retrograde and they lack farsightedness... They should change their outlook right now."

The Left, the Prime Minister said, has been consistently misinterpreting the nuclear agreement. They had also opposed the Green Revolution, he said.

"The nuclear agreement is in national interest. We understand that if nuclear energy cannot be generated at an appropriate price, the country's development will cease to take place," Singh said, adding "the CPI(M) is misleading the people on the agreement."

He said the "nuclear agreement is an issue where Left policy will be proved wrong in future and the Left will also realise it. I advise the Left parties to change their outlook."

Singh alleged that the CPI(M) had joined hands with the BJP on the nuclear issue in the Lok Sabha and its position was to oppose economic and foreign policies.

He also attacked the CPI(M) for its efforts to push the Third Front. "CPI(M) is helping the BJP politically with its initiative for a Third Front, which will only divide secular votes," he said.

The Prime Minister said the Left are dividing secular votes "which is helping the BJP."

On the electoral prospects of Third Front, he said "there is no possibility" of it coming to power at the Centre "as the constituent parties have no common programme ... They are only working to oppose us on every issue."

The Prime Minister also slammed the Left Front government of West Bengal, saying its policies had led to "under-development" of the state.

He said the "Congress had recently prepared a report on West Bengal government's 30-year tenure. It revealed that how due to the state government's wrong policies, West Bengal has remained underdeveloped. I fully agree with the report card."