Three senior peers have quit the Labour whip amid continuing controversy over anti-Semitism within its ranks.
Lord Triesman, a former Labour general secretary and foreign office minister, said the party and its leadership are “institutionally anti-Semitic”.
Lord Darzi, a former health secretary, said he had “zero tolerance” for anti-Semitism or any other form of religious or racial discrimination.
Lord Turnberg said he feared for Labour’s future due to the “overt” anti-Semitism that “permeates the party machine”.
Labour insisted it was taking “decisive action” against the “tiny minority” of members who had been involved in alleged anti-Semitism.
The resignations came as the party is braced for a major BBC Panorama investigation into its handling of the issue.
In his letter of resignation, Lord Triesman, a former chairman of the Football Association, said he was quitting as the extent of anti-Semitism among the “top leadership” had became clearer day by day.
“Anti-Semites are shielded and solid serious party members are thrown out unceremoniously,” he wrote in a letter to the Labour leader in the Lords, Baroness Smith.
“And each new manifestation is followed by a grim parade of social media messages directed at Jewish party members. The experience of life in the party has become sickening.
“My decision is straightforwardly about the party leadership’s use of any excuse to allow their allies to attack Jews or engage with anti-Semites.
“My sad conclusion is that the Labour Party is very plainly institutionally anti-Semitic, and its leader and his circle are anti-Semitic having never once made the right judgment call about an issue reflecting deep prejudice.”
He added: “We may one day be the party of anti-racism once again but it certainly isn’t today.”
Lord Darzi, whose family was caught up in the 1915 Armenian genocide, said that he would now be sitting in the Lords as an independent.
“I have zero tolerance to anti-Semitism, Islamophobia or any other discrimination against religion or race. This decision has not been lightly taken,” he told BBC2’s Newsnight.
Lord Turnberg told the programme: “It is not just the policies on foreign affairs – pro-Russia, pro-Venezuela, anti-America – and not just Brexit vacillation and bypassing parliamentary opinion, but the overt anti-Semitism that permeates the party machine that is no longer possible for me to tolerate.
“I fear for the future of this party to which I have devoted myself for so many years.”
Labour rejected the “false and offensive” claims made by the peers and defended its response to the anti-Semitism allegations which have dogged the party in recent years.
A spokesman said: “The Labour Party at all levels is implacably opposed to anti-Semitism and is determined to root out this social cancer from our movement and society.
“Labour is taking decisive action against anti-Semitism, doubling the number of staff dedicated to dealing with complaints and cases.
“And since Jennie Formby became general secretary, the rate at which anti-Semitism cases have been dealt with has increased four-fold.
“Our records show that anti-Semitism cases that have gone through the stages of our disciplinary procedures since September 2015 account for about 0.06% of the party’s membership.
“This represents a tiny minority, but one anti-Semite is one too many, and we will continue to act against this repugnant form of racism.”