LONDON (Reuters) - Pro-European Union rebels were threatened with a general election this summer if they defeated Prime Minister Theresa May’s Brexit plans on customs, a lawmaker said on Wednesday, threatening to widen rifts in the PM’s party.

FILE PHOTO - Britain's Prime Minister, Theresa May speaks at the Farnborough Airshow, in Farnborough, Britain July 16, 2018. Matt Cardy/Pool via REUTERS

Conservative whips, who enforce discipline in the party, threatened to call a confidence vote that could bring down the government before a crucial vote on Tuesday on customs, one lawmaker told Reuters. Rebel lawmaker Anna Soubry told BBC radio that the prospect of a national election was also raised.

“It was an appalling spectacle,” Soubry told BBC Radio 4, adding she had told a senior whip to “bring it on”.

“These nonsenses of threatening general elections, and votes of confidence in the prime minister ... bring it on, because I shall be the first in the queue to give my vote of full confidence in the prime minister,” Soubry said. “Problem is, I don’t think she’s in charge any more.”

Conservative lawmakers fear an election, and the possible victory of veteran socialist Jeremy Corbyn. Earlier this month, his Labour Party took a lead in the polls.

Labour also says the June 2016 referendum vote to leave the European Union must be respected but has attacked the PM over the splits in her party.

In one of the most tumultuous periods in recent British political history, there have been four major votes in the past four years: the Scottish independence referendum of 2014, the 2015 UK election, the Brexit referendum of 2016 and the snap election called by May last year.

May narrowly avoided a defeat in parliament at the hands of the pro-EU lawmakers from her own party in Tuesday’s vote, helped by four opposition Labour lawmakers who went against their party to support the government. Turmoil over Brexit plans has hit the pound.

Parliament voted 307 to 301 against an amendment to trade legislation that would have required the government to try to negotiate a customs union arrangement with the EU if, by Jan. 21, 2019, it had failed to negotiate a frictionless free trade deal with the bloc.

On Monday, May infuriated Conservative lawmakers who want to keep the closest possible ties with the EU when she decided to accept a number of demands by hardline pro-Brexit MPs from her party.

That came after she had fought hard to get the agreement of cabinet ministers at her Chequers country residence earlier this month for her vision of Brexit. The cabinet deal was then undermined by the resignations of Brexit minister David Davis and Foreign Secretary Boris Johnson.