Hilary Armstrong, Chancellor of the Duchy of Lancaster, indicated during the Bill's second reading on Monday that the Government would resist any attempts to change the way public benefit is defined in the Bill.
Rebel Labour backbenchers or the Lib Dems are likely to table amendments at committee stage to strengthen the public benefit test. But Armstrong said the Government continued to back a universal assessment of public benefit, which the Charity Commission would implement according to current case law.
The Bill proposes to remove the presumption that charities working to advance education or religion or to relieve poverty are of public benefit, and to replace this with a system where charities need to fulfil one of 12 charitable purposes and show their activities benefit the public. The Charity Commission has indicated it would like further clarification.
Armstrong said that by being more specific, for example with public schools, the Government ran the risk of excluding organisations it did not want to exclude.
"Clarity in one aspect may bring a lack of clarity in others," she said, adding that the same principle would apply to all fee-charging charities "whichever sector they operate in".
Andrew Turner, the shadow charities minister, said the Conservatives would support the Government in voting down any amendments that called for a more onerous test for public benefit.
But he argued against the Bill's proposal to remove the presumption that educational, religious and poverty charities are for the public benefit.
In its current form, the Bill makes some such charities that have been operating for hundreds of years "guilty until proved innocent", he said.
Turner argued that by forcing charities to prove their work is for the public benefit, the Government would introduce an unnecessary and in some cases costly administrative burden on many organisations.