The senior Tory figure has effectively dared Mr Sunak to sack him by announcing that he is supporting the right-wingers who are pushing for last-minute changes to the deportation legislation.
Mr Anderson announced on X, formerly known as Twitter, that he was backing the hardline amendments tabled by Bill Cash and Mr Jenrick.
“I have signed the Cash & Jenrick amendments. I will vote for them,” the controversial MP for Ashfield in Nottinghamshire tweeted.
Asked by if the Tory whips have told him he can still remain in his role as deputy chairman, Mr Anderson told reporters: “No, I haven’t been told that.”
Although he did not immediately resign from the job, Mr Anderson’s allies believe he is more likely to quit before he is fired by Mr Sunak over the act of rebellion.
The Rwanda Bill.
I have signed the Cash & Jenrick amendments.
I will vote for them.
— Lee Anderson MP (@LeeAndersonMP_) January 15, 2024
Earlier on Monday, grilled on whether he would sack Mr Anderson if he rebelled, Mr Sunak said only: “I’m frustrated about the situation ... I’m confident that the bill we’ve got is the toughest that anyone’s ever seen.”
Hardline MPs are vowing to vote against the government if Mr Sunak refuses to back down by Wednesday’s vote – with one telling The Independent that the chances of a seismic defeat that could end his time at No 10 are “under-priced”.
It would take just 29 Tory MPs to overturn Mr Sunak’s 56-seat parliamentary majority and defeat the government at the final Commons vote on Wednesday.
As well as trying to block any role for the European court in deportation cases, Mr Jenrick and others have demanded that Mr Sunak restricts the grounds on which illegal migrants can bring claims.
Hardliners in the New Conservatives and the European Research Group (ERG) met on Monday to discuss their amendments ahead of the crucial third reading showdown.
One senior right-wing Tory MP involved in the discussions said there was a “growing feeling it is better not to have any bill than a bill that doesn’t work”.
And John Hayes, chair of the Common Sense Group, told The Independent: “There is significant support for the amendments – it’s more than I think the government were anticipating. I’m hopeful the government will listen.”
In an apparent bid to keep right-wingers happy, the Tory leader talked up his willingness to use the bill to ignore any injunctions from the European Court of Human Rights on Rwanda deportations flights.
Mr Sunak told GB News: “If you’re asking me … are there circumstances in which I’m prepared to ignore those rule 39s [section 39 injunctions]? Then yes, of course there are.”
No 10 refused to comment on any conversations with Mr Anderson or cabinet minister Kemi Badenoch, who is said to have warned the PM’s team that the bill does not go far enough.