As recently as Friday, Sir Keir had been saying the investigation into her comments was not “resolved”.
Conservative Party chairman Richard Holden said it was “inconceivable” that the Labour leader “wasn’t told the process had finished and a warning issued”.
Questioned about the situation earlier, Sir Keir told reporters that “the process overall” was “obviously a little longer than the fact-finding exercise”.
Ms Abbott, who became the first black woman to be elected to Parliament in 1987, was a close ally of former Labour leader Jeremy Corbyn and served as his shadow home secretary.
Mr Corbyn, who was suspended as a Labour MP in 2020 for saying the scale of antisemitism within Labour’s ranks had been “dramatically overstated” by his opponents, has confirmed he will stand against the party.
He will contest Islington North, which he has held since 1983, as an independent candidate. A complete list of candidates standing in the seat will be available on the BBC website after nominations close.
Momentum, the left-wing campaign group set up support Corbyn’s leadership, said it would be “outrageous” for the party not to pick her as its candidate, having readmitted her as an MP.
“Anything less is a slap in the face to Diane, her constituents and the millions inspired by her example,” it added.
Labour’s full list of candidates is set to be endorsed at the NEC on Tuesday next week.
Parliament is due to be formally shut down on Thursday, triggering the official five-week election campaign ahead of polling day on Thursday 4 July.
