Three Conservative MPs have resigned from the party and joined The Independent Group.

The trio - Heidi Allen, Anna Soubry and Sarah Woollaston wrote a joint letter to Prime Minister Theresa May to inform her of their decision.

The explosive letter condemned the "Government's disastrous handling of Brexit", saying that the issue had "re-defined the Conservative Party."

The pro-remain trio pointed to a "shift to the right" within their former party and said that the European Reform Group within the party had undone the efforts to modernise it.

The letter said: "We no longer feel we can remain in the Party of a Government whose policies are so firmly in the grip of the ERG and DUP."

They added: "A purple momentum is subsuming the Conservative Party as much as the hard left has been allowed to consume and terminally undermine the Labour Party."

Reacting to the news, the Prime Minister tweeted that she was "saddened b the decision."

She said: "These are people who have given dedicated service to our party over many years and I thank them for it.

"Of course, the UK's membership of the EU has been a source of disagreement both in our party and our country for a long time. Ending that membership after four decades was never going to be easy.

Citing the need to deliver on a manifesto promise to deliver on the decision of the British people to leave the EU, Mrs May said her party was "doing the right thing for our country."

She added: I am determined that under my leadership the Conservative Party will always offer the decent, moderate and patriotic politics that the people of this country deserve."

Despite only being formed on Monday when seven Labour MPs resigned from their part, The Independent Group now has as many MPs as the Liberal Democrats.

The seven said that "politics is broken" and launched a website and twitter feed under the hashtag #changepolitics

An eighth Labour MP, Joan Ryan, joined Chukka Umunna, Luciana Berger, Mike Gapes, Chris Lesliw, Angela Smith, Anne Coffey and Gavin Shuker, in leaving her party on Tuesday evening.

 READ MORE: Seven MPs quit the Labour Party in protest 

While not a formal political party, The Independent Group are the joint fourth biggest group in the Commons, joining the Liberal Democrats with 11 MPs.

The current Conservative government now has 314 members, the Labour Party 247 with the Scottish National Party the third biggest with 35 MPs.