Seven Labour MPs quit the party on Monday, 18 February, saying they no longer had confidence in Corbyn and claiming the party had been "hijacked" by the far left.

Three Conservative MPs have resigned from the party to join eight former Labour MPs in the new Independent Group. Heidi Allen, Sarah Wollaston and Anna Soubry — who are all staunch Remainers — left the Tory Party after months of criticising Theresa May and her approach to Brexit.

The Independent Group now has 11 members, more than the Liberal Democrats. ​The latest Labour MP, Joan Ryan, quit on Tuesday night, complaining about anti-Semitism.

In a letter to the Prime Minister, the Tory defectors said the Conservative Party was "in the grip" of the European Research Group — which supports a hard Brexit — and the Democratic Unionist Party.

​"Brexit has redefined the Conservative Party — undoing all the efforts to modernise it," they claimed. "We find it unconscionable that a party, once trusted on the economy, more than any other, is now recklessly marching the country to the cliff edge of no deal," they wrote in the letter.

May responded with an uncharacteristic splurge of tweets in which she thanked the three MPs for their "dedicated service" but promised to delivering on the manifesto commitment to deliver Brexit and implement "the decision of the British people".

Soubry represents Broxtowe in Nottinghamshire, while Allen is MP for South Cambridgeshire and Wollaston's seat is Totnes in Devon. All are Tory strongholds and the Independent Group would be unlikely to win them in a general election.

​In 1981 several MPs broke away from Labour and formed the SDP. On that occasion only one Conservative MP joined them, although Chris Grayling was among those who supported the SDP as an activist.

On Tuesday night, another Tory MP Sam Gyimah, who resigned as a minister over Brexit, denied he planned to join the Independent Group.

"I hugely admire Luciana Berger's brave stance against antisemitism. But, ultimately, this is a Labour Party matter and is nothing to do with me," he said.

​Whether his stance will change after Wednesday's move remains to be seen. Two other Tory MPs highly critical of May's Brexit strategy — Nick Boles and Antoinette Sandbach — have previously ruled out quitting the party. 

​The Independent Group will vote as a bloc against a no-deal Brexit or a hard Brexit and will push for a second referendum and will be supported by the Liberal Democrats and the SNP but both Labour and the Conservatives say they are in favour of Brexit and will respect the will of those who voted in the 2016 referendum.