In a further sign of differences between the Left parties, the Communist Party of India-Marxist (CPI-M) and the Communist Party of India (CPI) will attend the ruling United Progressive Alliance's (UPA) fourth anniversary dinner on Thursday. But their smaller allies, the Forward Bloc and the RSP, will stay away.

Sources in the CPI-M confirmed that its General Secretary Prakash Karat, politburo members Sitaram Yechury and Brinda Karat and party MPs in town would attend the dinner at Prime Minister Manmohan Singh's residence.

Accompanying them would be CPI leaders, including general secretary A B Bardhan and D Raja.

However, the Revolutionary Socialist Party (RSP) and Forward Bloc leaders said they would skip the function because attending it would smack of hypocrisy.

"On Friday, Left parties meet to discuss the strategy on an agitation programme against the UPA government and its policies. We don't think it is proper to attend a dinner hosted by the UPA the evening before," G Devarajan, National Secretary of the Forward Bloc said.

The relationship between the CPI-M, which leads the Left parties, and its smaller partners have hit a new low after bloody clashes during the recent local self-government polls in the Left Front ruled West Bengal.

The Forward Bloc and the RSP have also been miffed with the CPI-M in particular for its green signal to the central government on negotiations with the International Atomic Energy Agency (IAEA) in connection with the India-US civil nuclear deal, which the Left has opposed vehemently.

The dinner comes at a time when ties between the Congress-led UPA and the Left parties, which prop the Manmohan Singh government, have soured on issues like price rise.

On Friday, the four Left parties will meet to discuss new strategies to put the government on the mat over its failure to check rising food prices.

The controversial celebratory dinner at the prime minister's house will also be boycotted by Uttar Pradesh's ruling Bahujan Samaj Party (BSP). But the Samajwadi Party has agreed to attend, a sign of the thaw in its relations with the Congress.