Liberal Democrat MPs could block boundary changes as payback for a failure over Lords reform, Simon Hughes has warned.
The Lib Dem deputy leader threatened "consequences" if Tory rebels do not fall into line over the proposals to make the Lords an 80% elected second chamber.
Last night the Commons passed the Lords reform bill's second reading by 462 votes to 124, securing a massive majority of 338.
But David Cameron and Nick Clegg had to rely on Labour votes to secure approval of the legislation, however, as the coalition suffered its largest ever rebellion in the 22:00 vote.
Ninety-one Tory backbenchers revolted - significantly more than the 81 who rebelled against the government on calls for an EU referendum last October.
The night was marked by high drama, with reports of the prime minister jabbing his finger at Tory rebel leader Jesse Norman, who was then forced to leave the parliamentary estate following threats from his own party whips.
Hughes told the Today programme that the Lib Dems had stuck by their side of the "deal" – and that they expected the Tories to do the same.
"We are clear you can't have a deal broken by one side without consequences," he said.
"There would be consequences if they broke it. We haven't reflected on that at all, but the one thing the Tories desperately want is boundary changes which is advantageous to them. We honoured the deal, it is up to them how they do it."
Conservatives say the dramatic shakeup of Britain's electoral map, which could hand the party around a dozen more seats at the general election, was a quid pro quo for the electoral reform referendum, which took place in May 2011.
Coalition tensions are running extremely high as a result. Ministers were forced to abandon a key vote guaranteeing the passage of the Lords reform bill through the Commons over a 14-day period after it became clear it would have been roundly defeated by Tory rebels voting with the Labour party.
"Over the summer, the Labour party has to come clean on its commitment to reform and the Tory party have to work out… how they deliver the deal," Hughes added.
Backroom negotiations will now get underway as an attempt is made to secure the reform.
But Labour's demands for a referendum on the change, a call the coalition has so far resisted, means agreement is far from guaranteed.
Yesterday evening Clegg emailed Lib Dem activists to tell them the second reading result was a "huge triumph for our party".
"We have been reasonable and looked at acceptable compromises at every stage," he said.
"That is why we agreed to withdraw today's timetabling motion, to allow the Conservative team in government take more time over the summer to talk to their backbench colleagues."
He added: "When we return in the autumn to vote on this again, we fully expect the Conservatives to deliver this crucial part of the coalition deal - as we have delivered other coalition policies."