The Labour MPs Hazel Blears and David Blunkett have written to the government asking for an extension to the deadline for spending money remaining in the £70m Communitybuilders fund.
Communitybuilders was set up by the Communities and Local Government department under the Labour administration to provide loans and grants to community-led organisations, and is managed by the Social Investment Business.
In October last year, the SIB wrote to applicants saying that any money they received must be spent by the end of March. At that point, £28m of Communitybuilders funds was unspent.
The joint letter from Blears and Blunkett to ministers at the CLG calls for organisations to be given additional time to spend the money.
An SIB spokeswoman said she expected charities receiving cash from the fund to have spent all available money by the end of March, but it would be useful for applicants to have more flexibility about their timescale.
Andrew Stunell, a Liberal Democrat minister in the CLG, said in a recent answer to a parliamentary question that the government was considering other options "to maximise the flexibility of the fund and secure the best value for money".
He said the government was "actively considering an endowment approach" to giving out funds, but further consultation was required.