Nick Clegg's "dirty" decision to torpedo Tory plans to redraw the electoral map was a "shattering blow" to the party, a former Conservative cabinet minister has admitted.
In August 2012 the deputy prime minister decided to kill off legislation that had already passed Commons that would have cut the number of MPs from 650 to 600 and created new constituencies. David Cameron and the Tories were seen as more likely to be able to win the next election under the new map.
Clegg decided to block the changes in revenge for the prime minister being unable to get enough Tory backbenchers to support the Lib Dem dream of a largely elected House of Lords. "I cannot permit a situation where Conservative rebels can pick and choose the parts of the contract they like, while Liberal Democrat MPs are bound to the entire agreement," he said at the time.
Lord Strathclyde, who was leader of the House of Lords from 2010 until January 2013, denounced Clegg's move as "an outrage" on Wednesday. The veteran Tory peer made the comments while speaking to a House of Lords committee for the first time since he left government. He said Clegg had agreed to sign off on the new map in exchange for a referendum on the Alternative Vote - which had been granted.
"It was extraordinary behaviour, we had come to this agreement," he said. "It was completely understood what was going on. There would be a referendum and there would be a boundary commission to work on a fairer system for parliamentary seats."
"And to see this stymied, pulling the rug away from us at the very last moment almost on a parliamentary ploy ... really was a terrible and dirty trick."
A clearly still angry Strathclyde added: "'Dirty trick' doesn't emphasise it strongly enough."
Clegg's decision to prevent the electoral map being redrawn could make the difference between a Tory victory or defeat in 2015. The Conservative Party argues the current arrangement is unfair, as the party has to win a greater share of the national vote in order to win the same number of MPs as Labour.
Polls have largely shown a consistent lead for Ed Miliband and Labour over the past year. With the election to be held on the same seats as in 2010, the Conservatives have an uphill battle to secure a majority - something the party did not manage last time around. The change to the map was also likely to have hurt the reelection chances of several Lib Dem MPs.
"The Lib Dems looked at the maths, they got their clever people to look at it, they wanted the incumbency factor at the next election and decided they couldn't do it. The prime minister had no choice," Strathclyde said.
He insisted Cameron had relied on the "good faith" of Clegg to stick to the original agreement. "We believed in our souls as Conservatives that by giving referendum we would get the reduction [in seats]. It was a shattering blow."
However despite his strong words on Clegg, he said the coalition "overall" had worked and that he expected it to last right up until the general election in 2015.