Conservative MPs rounded on Boris Johnson after it emerged that the US ambassador had decided to resign in the wake of the senior Tory's lack of support.
Sir Kim Darroch said his job had become “impossible” after the leak of diplomatic memos highly critical of Donald Trump’s administration.
His decision is understood to have been made after Mr Johnson repeatedly refused to support him during a televised Tory leadership debate on Wednesday.
Meanwhile, Labour denied claims senior figures in the party interfered with anti-semitism complaints as a BBC Panorama documentary was set to air at 9pm.
A Labour spokesman accused the broadcaster of “pre-determining” the outcome of its investigation – while the broadcaster claimed the party was “criticising a programme they have not seen”.
See below for live updates
Welcome to The Independent's politics liveblog, where we will be bringing you the latest updates throughout the day.
Here is today's front page:
A juicy story to start the day.
John Major says he will launch a judicial review to stop Boris Johnson shutting down parliament to force through a “totally unacceptable” no-deal Brexit.
The former Conservative prime minister condemned the Tory leadership favourite for failing to rule out prorogation – which he likened to the actions of Charles 1 in the 1640s.
Tory Brexiteers were guilty of championing parliamentary sovereignty “except when it is inconvenient for Mr Johnson”, Sir John said.
Labour should change its rules to automatically throw out members if there is clear evidence of antisemitism, a senior shadow minister has urged.
Sir Keir Starmer said the party had to do "whatever is necessary" to win back critics who had deserted Labour over its handling of anti-Semitism claims.
His comments came after three senior peers quit the Labour whip in protest at the handling of the issue under Jeremy Corbyn's leadership.
Labour is braced for further revelations in a potentially damaging BBC Panorama investigation on antisemitism in the party which is due to be aired on Wednesday night.
Lord Triesman, a former Labour general secretary and foreign office minister, said the party and its leadership are "institutionally anti-Semitic", while Lord Darzi and Lord Turnberg also quit the Labour whip.
Sir Keir said it was "very easy for people in leadership positions" in the shadow cabinet to "duck responsibility".
He told BBC Radio 4's Today programme: "I think we have got to take decisive action.
"Firstly, I would support a rule change that says you expel in clear cases of antisemitism automatically, just as we do for people who support another political party an election.
"Secondly, be very clear if you deny we've got a problem, that's part of the problem.
"Thirdly - and this is a cultural and attitude issue - now the Equality and Human Rights Commission is looking at the Labour party, we should throw open the books and say 'you've got access to anything, you have got access to any member of staff, we have made some process changes which have improved things but we have still got a problem, help us through this'.
"Many organisations circle the wagons when they are challenged. That is the wrong approach, we have got to be very, very open."
Pro-EU political parties are set to take a major step towards forming a national “Remain alliance” by working together with a new organisation designed to increase the number of anti-Brexit MPs.
Independent MP Heidi Allen, who quit the Conservative Party earlier this year, will launch the “Unite to Remain” group on Wednesday, Ben Kentish reveals.
Heidi Allen, a former Change UK MP who now sits as an independent, discusses her attempts to form a pro-Remain alliance.
Team Boris has hit back at John Major, with sources saying he has "gone completely bonkers" over threat of judicial review.
"He's clearly been driven completely mad by Brexit."
John Major's threat of legal action if Boris Johnson prorogues parliament has been welcomed by former Labour Lord Chancellor Charlie Falconer, a respected QC.
Ex-Labour MP John Woodcock has joined The Independents - *another* twist in the journey of The Independent Group/Change UK.
He joins Heidi Allen, Luciana Berger, Gavin Shuker and Angela Smith for the group, which is a "workers collective" rather than a political party.
It comes after Labour and Tory MPs quit their parties in February in protest over issues such as Brexit and handling of antisemitism by Jeremy Corbyn.
At first they sat as independent MPs, known as the Independent Group (TIG) before becoming Change UK to stand in the European Parliament elections.
Meanwhile, half of the splitters decided to leave Change UK - Chuka Umunna, Sarah Wollaston, Allen, Berger, Shuker and Smith.
Anna Soubry became the new Change UK leader, with Joan Ryan, Chris Leslie, Mike Gapes and Ann Coffey staying put.
However a legal challenge from the petitions website Change.org forced the group to change its name to The Independent Group for Change.
Umunna joined the Liberal Democrats while Wollaston remains an independent.
Our sketchwriter Tom Peck has written an excoriating piece on last night's TV leadership debate, where he says Boris Johnson would "dissolve on contact with the truth"
Read his piece here:
Britain's Next Prime Minister: The ITV Debate was watched by an average of 4.3m viewers. According to viewing figures from ITV, the debate had a peak audience of 4.7m viewers.
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