The investigation found evidence of “political interference” by the former leader’s office in the complaints process.
Sir Keir said that he wanted to be able to “draw a line in the sand” following the report. But Mr Corbyn rejected some of the equality watchdog’s findings and claimed the issue had been “dramatically overstated for political reasons” by his critics.
Soon afterwards, a Labour spokesperson announced Mr Corbyn had been suspended from the party pending an investigation. The whip was also removed.
Speaking to ITV’s Good Morning Britain on Friday, Sir Keir said: “I was very disappointed. A difficult decision was then taken yesterday in relation to his suspension, which I fully support.
“It was a difficult decision, as you can imagine. It was the right decision, it was the general secretary’s decision using the powers that he’s got.
“But leadership sometimes involves difficult decisions, and that’s why I set out my response in the way that I did.”
Sir Keir added: “I want to unite the party. Factional fighting has been a real problem in recent years and I stood as leader of the Labour Party on the base of uniting the party and driving factionism out of it.”
The Labour leader said he had spoken to Mr Corbyn the evening before the EHRC’s report being published to advise him as to how he would respond but has not spoken to him since.
“I set out how I would approach the response to the report, the findings in the report were very clear in my view about unlawful indirect discrimination and I thought it was absolutely right that we accepted the findings, apologised for the hurt and the pain and made it clear we would implement all the recommendations,” he said.
Charlie Sayt to Keir Starmer: Is Jeremy Corbyn anti-semitic?
Sir Keir told Sky News that deputy leader Angela Rayner and himself were both “really disappointed” with Mr Corbyn’s response.
“This was a day, I had hoped, where the Labour Party could draw a line, a painful day of course in light of the findings, but draw a line and move forward,” he said.
“And I know that’s what Jewish communities wanted. They wanted us to accept the report and move forward on the recommendations.”
Sir Keir said while that was how he “hoped yesterday would play out”, he added: “It didn’t.”
Asked if a split was necessary to save the party from calls of anti-Semitism, Sir Keir added: “I don’t think it’s necessary, and I don’t think it will happen.”
In a statement just after 1pm on Thursday a Labour party spokesperson said: “In light of his comments made today and his failure to retract them subsequently, the Labour Party has suspended Jeremy Corbyn pending investigation.
“He has also had the whip removed from the Parliamentary Labour Party.”
Mr Corbyn has said he will “strongly contest the political intervention to suspend me” from the party.