Taxpayer should contribute £23 million a year to political parties

Extra state cash - the equivalent of 50p per voter - would make up for a £10,000 cap imposed on individual donations and restrictions on trade union funds.

A 15-month inquiry by the Committee on Standards in Public Life concluded there was no credible alternative way to remove the influence of "big money" on politics.

But the latest effort to reform the scandal-hit Westminster system looks set to become mired in the same party disputes that have scuppered previous attempts.

In dissenting notes included in the report, senior Tory and Labour members renewed objections to fundamental elements of the proposed package.

Labour former Cabinet minister Margaret Beckett said she had "grave concerns" over moves to force individual trade union members to "opt in" to the payment of fees to the party.

And Tory Oliver Heald criticised the rejection of his party's call to set the cap much higher, at £50,000. The moves could lead to significant reductions in each party's income.

In a letter to Prime Minister David Cameron setting out the proposed changes, committee chair Christopher Kelly said it had "come to the conclusion that the only safe way to remove big money from party funding is to put a cap on donations, set at £10,000".

He conceded that it was "hard to imagine a more difficult climate" in which to suggest the public should pay more towards political parties.

"We would not have made it if we thought there was a credible alternative. We do not believe there is.

"If the public want to take big money out of politics, as our research demonstrates they do, they also have to face up to the reality that some additional state funding will be necessary."

The sum required should be "kept in perspective", he said, as it was "little more than the current cost of a first class stamp" for each voter per year.