Sir Keir said he would not let “a focus on one individual to prevent us from doing the vital work of tackling anti-Semitism” and vowed to make the party “a safe place for Jewish people”,.
A five-strong panel of Labour’s National Executive Committee voted to reinstate Mr Corbyn on Tuesday. He had been suspended and had the whip withdrawn for his response to a damning Equality and Human Rights Commission’s report which found Labour had acted unlawfully in its handling of anti-Semitism complaints.
Mr Corbyn had said the scale of anti-Semitism in the party was “dramatically overstated for political reasons” by opponents and “much of the media”.
Earlier on Tuesday Mr Corbyn released a statement attempting to clarify the remarks. But the decision to reinstate him after 19 days has been met with fierce opposition and was branded “ridiculous” by veteran Labour MP Dame Margaret Hodge.
In a statement, Sir Keir said Mr Corbyn’s response to the ECHR “was wrong” and repeated his vow to set up an independent complaints process.
“I know that this has been another painful day for the Jewish community and those Labour members who have fought so hard to tackle anti-Semitism,” he said. “I know the hurt that has been caused and the trauma people have felt.
“Jeremy Corbyn’s statement in response to the EHRC report was wrong and completely distracted from a report that identified unlawful conduct in our tackling of racism within the Labour Party. This should shame us all.
“I will not allow a focus on one individual to prevent us from doing the vital work of tackling anti-Semitism. When I stood as leader of the Labour Party, I was clear that my first priority would be to root out anti-Semitism. It still is.”
He added: “I know we have a long way to go, but I am absolutely resolute in my determination to make the Labour Party a safe place for Jewish people. I stand by the commitments I made last month to accept the findings and the recommendations of the EHRC’s report in full.
“That must mean establishing an independent complaints process as soon as possible in the new year. This is my commitment and my promise to our party, the Jewish community and the British people.”
It is yet to be announced whether Mr Corbyn will have the whip restored. It has been reported a group of MPs have threatened to resign if Mr Corbyn is readmitted to the parliamentary Labour party.
Sir Keir’s comments came after Mr Corbyn called on Labour to “come together”.
“I am pleased to have been reinstated in the Labour Party and would like to thank party members, trade unionists and all who have offered solidarity,” the Islington North MP wrote on Twitter.
“Our movement must now come together to oppose and defeat this deeply damaging Conservative government.”
But the reinstatement sparked a fierce backlash from Jewish MPs and societies, including Labour former minister Dame Margaret Hodge.
She said she could not “comprehend” why it is acceptable for Mr Corbyn to be a Labour MP “if he thinks anti-Semitism is exaggerated and a political attack”.
She tweeted: “This is a broken outcome from a broken system. A factional, opaque and dysfunctional complaints process could never reach a fair conclusion. This is exactly why the EHRC instructed Labour to setup an independent process!”