Jeremy Corbyn was accused of being in denial about anti-Semitism in the Labour Party and "shooting the messenger" after suggesting a damning report on the issue was biased.
The Home Affairs Select Committee report found the Labour leader has failed to provide "consistent leadership" in tackling anti-Semitism within the party's ranks.
But responding, Mr Corbyn suggested it was biased against the party and described its sharp criticism of an inquiry into the issue by Labour peer Baroness Chakrabarti as "unfair".
The acting chairman of the powerful committee of MPs, Tim Loughton, said the Labour leader's reaction shows he is still failing to take the issue seriously.
The Tory MP told the Murnaghan programme on Sky News: "I'm afraid he's still in denial and that sort of response is deeply disappointing for all members of the committee."
He said the report investigated anti-Semitism within all political parties, adding: "This is not about trying to score points off Jeremy Corbyn and I'm disappointed that it seems to have been accepted by him in that manner because that doesn't do any of us any good."
The cross-party committee also questioned whether Mr Corbyn "fully appreciates" the nature of post-war anti-Semitic abuse.
Labour MP Pat McFadden insisted the report should be taken seriously.
Appearing to refer to the Labour leader, Mr McFadden said the party should not "fall into the trap" of pointing to its anti-racism record as proof that it could not have a problem with anti-Semitism.
"I hope we don't make the mistake here of shooting the messenger," he told BBC One's Sunday Politics.
"I hope we take the report seriously, and I hope we don't fall into the trap that sometimes I see when these accusations are wielded, that we point to anti-racism records and say, look at our virtue in our record here, t hat must mean we can't be anti-Semitic.
"Let me be clear about this: pointing to your own sense of righteousness is no excuse for nastiness or cruelty to someone else. So I think we should take this very seriously indeed."
In the report, Labour was accused of "incompetence" over its handling of high-profile allegations of anti-Semitism, including those involving former London mayor Ken Livingstone and Jackie Walker, who was recently removed as vice-chairwoman of the Corbyn-supporting Momentum group.
The chair of the Jewish Labour Movement said the "litmus test" of the party's response to anti-Semitism is whether it expels Mr Livingstone, who was suspended in April after arguing that Hitler had supported Zionism in the early 1930s.
Jeremy Newmark told Murnaghan: "One of the real litmus tests as to whether or not the party has moved on on the issue of anti-Semitism is whether or not, in a post-Chakrabarti Labour party there is still space for people like Ken Livingstone, who over an extended period of time almost built a career out of calibrating those kinds of insults to cause the maximum hurt, pain and offence towards Jewish people.
"The party was right to suspend him, that was a step in the right direction but now they need to finish the job."
Mr Newmark acknowledged Mr Corbyn's rhetoric on anti-Semitism has "got better", but called for concrete action and the implementation of the recommendations in the Chakrabarti report.
Mr Livingstone, meanwhile, told Sky News he was "simply stating historical fact" with his comments about Hitler, which were described by the committee as "unwise, offensive and provocative".
The committee welcomed the Chakrabarti inquiry set up by Mr Corbyn but expressed doubts about its independence since the former Liberty director subsequently joined Labour and accepted a peerage.
But Mr Corbyn claimed the inquiry "violated natural justice" by refusing Lady Chakrabarti's request to appear before it.
The Labour leader said: "The report's political framing and disproportionate emphasis on Labour risks undermining the positive and welcome recommendations made in it.
"Although the committee heard evidence that 75% of anti-Semitic incidents come from far-right sources, and the report states there is no reliable evidence to suggest anti-Semitism is greater in Labour than other parties, much of the report focuses on the Labour Party.
"As the report rightly acknowledges, politicising anti-Semitism - or using it as a weapon in controversies between and within political parties - does the struggle against it a disservice."