The NCVO is asking its members to write to their MPs and lobby for changes to the Lottery Bill, which is going through the Commons.
The umbrella body wants to put pressure on ministers to include a clause to guarantee that 60 to 70 per cent of 'good causes' money from the lottery should go to voluntary sector bodies.
It also wants new limits on the power the Bill gives to ministers to control the amounts, purposes or periods of lottery funding, and a guarantee that the sector be consulted about lottery funding.
The Government has refused to make concessions on these points at the second reading of the Bill and in committee stage. The NCVO is providing members with a sample letter to send to MPs.
The Big Lottery Fund has given a commitment that 60 to 70 per cent of lottery funding will go to the sector, but the NCVO says this should be in the legislation.
It also argues that ministers should be given power to issue guidance to lottery distributors, making a distinction between core government spending and lottery funding.