Jeremy Corbyn said he did not accept all of the Equality and Human Rights Commission's findings and added that the scale of the anti-Semitism problem in Labour was "dramatically overstated" for political reasons, "by our opponents inside and outside the party, as well as by much of the media".
The EHRC identified serious failings in the Labour Party leadership in addressing anti-Semitism and an inadequate process for handling anti-Semitism complaints.
In a statement posted on Facebook, he said:
"Anti-Semitism is absolutely abhorrent, wrong and responsible for some of humanity's greatest crimes. As Leader of the Labour Party I was always determined to eliminate all forms of racism and root out the cancer of anti-Semitism. I have campaigned in support of Jewish people and communities my entire life and I will continue to do so.
"The EHRC's report shows that when I became Labour leader in 2015, the Party's processes for handling complaints were not fit for purpose. Reform was then stalled by an obstructive party bureaucracy. But from 2018, Jennie Formby and a new NEC that supported my leadership made substantial improvements, making it much easier and swifter to remove anti-Semites. My team acted to speed up, not hinder the process.
"Anyone claiming there is no anti-Semitism in the Labour Party is wrong. Of course there is, as there is throughout society, and sometimes it is voiced by people who think of themselves as on the left.
"Jewish members of our party and the wider community were right to expect us to deal with it, and I regret that it took longer to deliver that change than it should.
"One anti-Semite is one too many, but the scale of the problem was also dramatically overstated for political reasons by our opponents inside and outside the party, as well as by much of the media. That combination hurt Jewish people and must never be repeated.
"My sincere hope is that relations with Jewish communities can be rebuilt and those fears overcome. While I do not accept all of its findings, I trust its recommendations will be swiftly implemented to help move on from this period."
Labour leader Sir Keir Starmer said the findings of the excoriating report represent a "day of shame" for the party and has promised to implement its findings in full.
Speaking at a press conference, Sir Keir said: "I found this report hard to read and it is a day of shame for the Labour Party.
"We have failed Jewish people, our members, our supporters and the British public.
"And so on behalf of the Labour Party: I am truly sorry for all the pain and grief that has been caused."
He promised to implement the report's recommendations, including the establishment of a new independent complaints procedure.