Deputy Prime Minister Nick Clegg has pulled out of an official visit to Latin America in an effort to ensure the coalition gets its legislation enabling a referendum to be held on voting reform.
Mr Clegg had been due to travel next week to Mexico and Brazil in a trip intended to boost trade links with the region.
However he has now decided to remain in Britain for a crucial Commons vote - due to be held on Tuesday - on the Parliamentary Voting System and Constituencies Bill.
Ministers need to get the legislation on to the statute book by next Thursday if the referendum on introducing the alternative vote (AV) for Westminster elections - a key Liberal Democrat demand in the coalition agreement - is to go ahead as planned on May 5.
The bill had been held up in the House of Lords where Labour peers have mounted a protracted rearguard action against the legislation, which also includes measures to redraw constituency boundaries and reduce the number of MPs.
It is now expected to complete its passage through the upper chamber on Monday and will then go back to the Commons the following day.
Downing Street denied that Mr Clegg's decision to put off his Latin America trip was a sign of nervousness about the outcome of the vote in the Commons.
"The Deputy Prime Minister is the lead minister on this subject. The usual principle is that Parliament takes precedence over other engagements," the Prime Minister's official spokesman said.
However ministers are seeking to overturn a number of Lords amendments - including one which would make the referendum result non-binding if the turnout is less than 40% - in the Commons.
It would be highly embarrassing for Mr Clegg if it failed to do so as a result of his absence on foreign business.Reuse content