Bowing to the Left pressure, the government is understood to have accepted certain proposals of its outside supporters to amend the pension bill including having public sector fund managers and the option of 100 per cent investment in government securities.

However, the Left parties insistence that the employees on retirement should get 50 per cent of the average of previous three years' monthly pay as pension, has not been accepted by the government, sources said.

The Left parties have also been demanding that the government should fill the shortfall if the pensioner fails to get this return from investment of the pension funds.

Prime Minister Manmohan Singh is understood to have conveyed this to top Left leaders at a dinner meeting two days ago that as many as 17 states have already implemented the New Pension System.

Meeting of chief ministers has also been convened by the Centre to discuss available option for investing funds from the NPS.

Left leaders were told by the Prime Minister that the Chief Ministers of 17 states have been seeking central intervention to settle the problem of parking the huge pension funds.