The chief executive of Acevo has warned the Charities Bill could give the Charity Commission “carte blanche to pursue agendas they were never meant to adopt”, while other sector bodies have also expressed serious concerns.

Sir Stephen Bubb’s comments come in advance of the second reading of the Charities Bill in Parliament tomorrow.

New regulatory powers proposed in the bill would enable the Commission to dismiss trustees, issue charities with official warnings, close charities down and oversee fundraising activities.

Acevo has written jointly with law firm Bates Wells Braithwaite, the Directory of Social Change and the Charity Finance Group, warning that the powers in the bill are too broad, while NCVO has written separately expressing similar concerns.

Earlier this week the Charity Law Association also expressed widespread reservations.

Acevo warned, in a statement accompany its joint letter, that the new proposals would give the regulator a “dangerous amount of discretionary power”.

“The additional powers to dismiss trustees are littered with landmines,” it said. “Trustees could be dismissed if they are deemed unfit or if their sacking is deemed to be in the public interest… But on what basis and by whom are trustees deemed to be unfit?”

The chief executive association highlighted a recent High Court case by advocacy group Cage, after the Charity Commission attempted to persuade two charities to promise to never again provide it with grant money.

Cage argued the Commission had overstepped its jurisdiction. The case was withdrawn but seen as a victory for Cage and funder the Joseph Rowntree Charitable Trust.

Today, Bubb called for MPs to revise the bill.

"We’ve already seen just what power the Commission has tried to gather to itself under existing legislation," he said.

"To date it has been subject to some checks and balances but as this Bill stands, it would give the Commission, and the individuals in it, carte blanche to pursue agendas they were never meant to adopt, nor indeed should.

“We present a united front with the Charity Finance Group, leading charity solicitors Bates Wells Braithwaite and Director of Social Change in making these representations.”

Yesterday NCVO called for MPs to act with caution on the new measures.

A spokesman for NCVO said the body was concerned about the regulator’s proposed warning powers which would give it “wide discretion with no right of appeal”.

“We don’t believe a robust approach to regulation is necessarily unreasonable but it must come with appropriate safeguards for those in the crosshairs, such as in the case of warnings, a right of appeal,” the spokesman said.

“We also say, following the inclusion of people on the sexual offences register in the list of those automatically barred from trusteeship, that it is particularly important that the Commission’s process for processing waivers from disqualification is efficient and effective, as the number significantly increases.”

Today the Charity Commission said the proposals for greater power in the bill had been “scrutinised at length in the House of Lords and received strong support”.

New warning powers would “fill a crucial gap” and provide a “simple, expedient, reasonable and proportionate way of dealing with lower levels of breaches”, it said.