The Commons speaker, Lindsay Hoyle, has sparked a fresh row by refusing to allow Diane Abbott ask a question during a heated session of prime minister’s questions, which was dominated by discussion of a Conservative donor’s comments about her. Abbott had sought to ask a question throughout the 35-minute session, during which MPs debated the comments made about her by Frank Hester, the Conservatives’ biggest donor. The Guardian revealed earlier this week that Hester once said Abbott made him “want to hate all black women” and that she “should be shot”, comments the MP has called frightening. Hoyle provoked groans in the chamber, however, by ending the session without having called on her, even after the Labour leader, Keir Starmer, and Stephen Flynn, the Scottish National party leader in Westminster, both used their questions to raise the controversy. Hoyle is already under fire over his decision last month to allow the Labour party to amend an SNP motion on Gaza – a decision which triggered anger on the SNP and Tory benches and prompted an unprecedented apology from the speaker himself. Abbott tweeted afterwards: “I don’t know whose interests the speaker thinks he is serving. But it is not the interests of the Commons or democracy.” Abbott remains suspended from the parliamentary Labour party over a letter she wrote to the Observer last year. A Labour party spokesperson said on Wednesday, however: “It would have been good to have heard from her today in PMQs when she was trying to get the speaker’s attention.” Marsha de Cordova, a Labour MP who challenged the prime minister on Hester’s comments, told the Guardian: “Convention is that everyone who is on the written order paper gets called first, and she wasn’t on the order paper. But sometimes you have to break convention. I would have liked to see her called.” Stella Creasy, another Labour MP, tweeted during the session: “Right now Diane Abbott is standing to ask a question in prime minister’s questions. As her safety is debated by others. Something very wrong if her voice isn’t heard today.” Afterwards, a spokesperson for Momentum, the leftwing campaign group, said: “It was a shocking failure from the speaker not to pick Diane Abbott for a question at PMQs, despite her repeated attempts.” A spokesperson for Hoyle said that he had not called Abbott because there had not been time to do so once he had gone through those listed on the order paper. “This week – as is often the case – there was not enough time to call all members who wanted to ask a question,” they said. Others, however, said the speaker had been weakened by the row over last month’s Gaza debate, where his decision to abandon convention to allow Labour to amend the motion sparked anger and even a parliamentary motion to remove him. By Wednesday, that motion had attracted 95 signatures, though none from Labour MPs. As prime minister’s questions finished, Flynn and Starmer approached Abbott to talk to her as she sat on the backbenches. According to an account of the conversation retweeted by Abbott herself, Starmer asked if there was anything he could do to help her, to which she replied: “Restore the whip.”