Talks on funding political parties have effectively broken down after 18 months of negotiations.
Sir Hayden Phillips chaired the cross-party talks.
The Conservatives and Labour have been unable to agree on setting limits on campaign spending and on donations.
Justice Secretary Jack Straw accused Tory leader David Cameron of being "unwilling to negotiate".
Shadow Cabinet Office Minister Francis Maude said Labour had refused to move on union funding. The Lib Dems accused the Conservatives of "walking away".
The Tories said trade union donations should be included within a £50,000 limit on donations from individuals and organisations.
Labour wanted an end to the use of Tory Lord Ashcroft's millions being targeted on marginal Labour/Lib Dem seats.
Mr Maude described the breakdown of talks as "an historic missed opportunity".
"Eighteen months ago we put forward really radical proposals that would really clean up party funding and start to restore the public's trust in the political process and party funding," he told the BBC.
"But I'm afraid we've come up against an absolute brick wall in the face of the Labour Party's refusal to make substantive moves on union funding.
"It appears that the Labour Party is still over a barrel, held there by the trade union barons. And they were willing to accept a cap on all donations except the bulk of the donations made by trade unions."
But, he added: "We stand ready, at a moment's notice, to reengage in the discussions if there is some movement."
Mr Straw, who has been heading the negotiations for Labour, said: "We greatly regret that these talks have been suspended as a result of the Conservative Party's unwillingness to negotiate on a draft agreement.
"We had understood that all parties had thought in good faith that this draft agreement was the basis of a comprehensive settlement.
"We will now take time to reflect on next steps."
David Heath, the Liberal Democrats' constitutional affairs spokesman, said: "It is in the interests of good politics in this country that we find a way to reverse the arms race in party spending and curb the flagrant abuses in the current system.
"Following the loans for peerages scandals that is clearly what the public expected us to do."
He added: "For the Conservatives to now, in effect, walk away is a tragedy and very short-sighted on their part."
Sir Haydn Phillips, who chaired the talks, said he would be publishing the draft agreement that had been put to the two parties in August, but on which they later failed to agree.
In a statement, he said: "I said at the outset of these talks that I believed that a consensus between the parties on future reform was both desirable and possible.
"Yet, despite progress on a number of issues, it became clear at the fifth session of talks held today that the parties would not be able to arrive at an agreement on an overall package of reform at present.
"I remain convinced that an agreement to reform party funding would be in the general public interest and I hope that all possible efforts will be made to achieve some consensus on a comprehensive package of reforms."
However, that sentiment was thrown into doubt by Labour general secretary Peter Watt, who said a comprehensive deal had been made "all but impossible" by the attitude of the Conservatives.
A government spokesman said it was "disappointed" that the talks had not reached a consensus.
"It is grateful to Sir Hayden Phillips for his skill and perseverance in chairing the talks. The government will now consider what steps to take next," he said.