Nick Clegg cancels South America trip for constituencies vote

Party managers decide he should stay to ensure government does not lose vote when it returns to Commons next week
Nick Clegg addresses students in London
Nick Clegg would have missed the constituencies vote had he gone ahead with his trip to South America. Photograph: Dominic Lipinski/PA

Nick Clegg has cancelled a high-profile trip to South America after peers rejected government plans for drawing up new constituencies that would shrink the House of Commons from 650 to 600 MPs.

The Lib Dem leader called off the trip at 9pm, moments after it became clear that the House of Lords had rejected the government's plans.

Clegg had been due to spend four days travelling from Brazil to Mexico, but party managers have decided that he and the three ministers accompanying him should stay to ensure the government does not lose the vote when it returns to the Commons next week. The decision suggests the government believes the vote could come down to a matter of single figures.

It was the government's fourth defeat in the upper house on the parliamentary voting system and constituencies bill.

Peers voted by 275 to 257, a majority of 18, to allow the Boundary Commission to vary the size of constituencies by a larger margin than the government's plans.

The prime minister wants to save money by equalising the size of all but two parliamentary constituencies to around 76,000 voters. The government says that constituencies should vary in size by no more than 5% above or below that figure.

Peers voted in favour of an amendment, tabled by the crossbench peer Lord Pannick, that would allow constituencies to be varied in size by 7.5% in "exceptional circumstances" to be determined by the Boundary Commission. The Pannick amendment was a compromise between the government and Labour, which wanted to vary constituencies by 10%.

Pannick said: "It is a compromise amendment that recognises that we are dealing with an important and a sensitive area of national life … This amendment recognises the strength of the competing arguments on both sides of the debate."

The defeat poses a more serious threat to the government's plans than a vote on Monday when Labour peers, crossbenchers and Tory rebels joined forces to amend the bill to make the planned referendum on electoral reform non-binding if turnout falls below 40%. The rebels had a majority of only one on Monday.

Labour MPs are likely to join forces with the coalition to overturn the 40% threshold in the Commons. The vote yesterday, which could lead to a larger House of Commons than under the government's plans, will be supported by Labour MPs when the bill returns to the Commons.

Lord Wallace of Tankerness, the Liberal Democrat advocate general, said the Pannick amendment would "put at risk" some of the main elements of the bill. Wallace said: "At the heart of this bill is the principle of trying to seek equal value – one vote, one value – and to do so so that new constituencies can come into effect for the next general election in 2015."

The government fears Pannick's amendment could slow down the redrawing of parliamentary constituencies, which could mean they will not be ready for the general election planned in 2015. That would mean the Commons would remain its current size and the first-past-the-post electoral system would be used even if the AV referendum is passed.