Diane Abbott has been suspended from the Labour party for a second time after saying she did not regret her past remarks on racism, as Keir Starmer once again attempted to reassert his grip over his backbenchers.

The veteran MP now faces an investigation over her defence of remarks more than two years ago that people of colour experienced racism “all their lives”, which was different from the “prejudice” experienced by Jewish people, Irish people and Travellers.

In a statement to Newsnight on Thursday evening, Abbott said: “It is obvious this Labour leadership wants me out. My comments in the interview … were factually correct, as any fair-minded person would accept.”

In the interview with the BBC earlier on Thursday, Abbott, the first black woman elected to parliament, had said: “Clearly, there must be a difference between racism which is about colour and other types of racism because you can see a Traveller or a Jewish person walking down the street, you don’t know.

“I just think that it’s silly to try and claim that racism which is about skin colour is the same as other types of racism. I don’t know why people would say that.”

The suspension was the latest sign that the prime minister intends to take a tougher approach to party discipline after being forced to U-turn over controversial welfare cuts after a massive rebellion by his MPs.

He insisted on Thursday that he will not be “deflected” from his mission to reform Britain after suspending the whip from four Labour MPs who repeatedly voted against the government, including on welfare reform legislation.

Starmer said the suspensions of Rachael Maskell, Neil Duncan-Jordan, Brian Leishman and Chris Hinchliff were not just about a single vote but the result of “repeatedly breaking the whip” and undermining Labour’s ability to fulfil its manifesto.

At a joint press conference with the German chancellor, Friedrich Merz, he was asked whether punishing the MPs made him look weak.

“We are elected in to change this country for the better, and that means we’ve got to carry through that change, and we’ve got to carry through reforms,” he replied.

“I’m determined that we will change this country for the better, for millions of working people, and I’m not going to be deflected from that.

“And therefore we had to deal with people who repeatedly break the whip, because everyone was elected as a Labour MP on the manifesto of change and everybody needs to deliver as a Labour government. This is about what we’re doing for the country.”

Abbott, who has the honorary title mother of the house as the longest-serving female MP in the Commons, first made her comments in a letter to the Observer in 2023 and was suspended from the party after Starmer said they were antisemitic.

Abbott wrote that Irish, Jewish and Traveller people “undoubtedly experience prejudice”. “This is similar to racism and the two words are often used as if they are interchangeable,” she said.

“It is true that many types of white people with points of difference, such as redheads, can experience this prejudice. But they are not all their lives subject to racism.”

She swiftly apologised and withdrew the remarks at the time, and was eventually readmitted, after a protracted investigation, in time to stand in the general election.

Labour sources said the decision to once again suspend Abbott, one of the most well-known leftwing figures in the country, was made swiftly, and that this time she was not offered an opportunity to retract her remarks.

It unleashed an angry response among sections of the party. The veteran John McDonnell said: “It is extremely bizarre that Diane Abbott gets suspended for an interview in which she forthrightly condemns antisemitism and racism in all its forms whilst no action is taken against those that inserted into Keir Starmer’s recent speech Enoch Powell’s racist language.”

Her longstanding ally Shami Chakrabarti said: “People who are writing ‘island of strangers’ speeches should be a bit slow to sit in judgment on Diane Abbott, who has been fighting racism all her life.”

Angela Rayner said she was disappointed that Abbott had defended the comments, saying there was “no place for antisemitism” within Labour.

The deputy prime minister, who last year paved the way for Abbott to be allowed to stand for the party again at the election, told the Guardian the comments represented a “real challenge” for Labour. Rayner said it was “not good” the MP had sought to back away from her earlier apology.

A Labour party spokesperson said: “Diane Abbott has been administratively suspended from the Labour party, pending an investigation. We cannot comment further while this investigation is ongoing.”

In her BBC interview, Abbott said she felt “a bit weary” of people labelling her antisemitic. She had “spent a lifetime fighting racism of all kinds and in particular fighting antisemitism, partly because of the nature of my constituency”. Her north London constituency of Hackney North and Stoke Newington is home to a large Jewish population.

Asked whether she felt she had been “hung out to dry” by the Labour leadership during the disciplinary process relating to her remarks, she said: “In the end, Keir Starmer had to restore the whip to me.

“I got tremendous support locally. We had a big rally on the steps of Hackney town hall. And in the end Keir Starmer and the people around him had to back off because of the support I had from the community.”

Abbott was readmitted to the party and allowed to stand as a Labour candidate after party officials failed to broker a deal by which she would get the whip back in return for standing down. The row dominated the early days of the general election campaign.

The decision to suspend the four other MPs also sparked a backlash from parts of the Labour left. Maskell publicly criticised the move. “On this occasion, I don’t think he’s got it right,” she told the BBC. “There needs to be a better reach-out to backbenchers to ensure that we are the safeguards of our government.”

Before her own suspension, Abbott criticised the treatment of backbenchers and called for more space for MPs to raise concerns about policy. Writing on social media, she said: “Silencing dissent is not leadership. It’s control.”

A senior Labour figure expressed frustration at what they saw as inconsistent discipline, telling the Guardian: “There were other ministers who helped stir this rebellion – including one who actively encouraged colleagues to sign the amendment. Why are they allowed to carry on?”

But Jess Phillips, a Home Office minister, defended the move, saying the MPs involved should not be surprised by the consequences. “There has to be an element of discipline otherwise you end up not being able to govern,” she told BBC Radio 4’s Today programme.

“Constantly taking to the airwaves and slagging off your own government – I have to say, what did you think was going to happen?”