Labour’s handling of anti-Semitism complaints is an “embarrassing mess” and represents a “political failure”, peers have told Jeremy Corbyn.
Lord Harris, who chairs Labour’s group in the Lords, said the party’s moral authority had been “diminished” and its anti-racism credentials dented.
Labour faces a possible probe by the human rights watchdog into whether it discriminated against Jewish people.
Mr Corbyn said on Friday that the party had “nothing to hide”.
The Labour Party has been dealing with complaints of anti-Semitism over the last two years.
Senior figures have clashed in the past week over the way the backlog of anti-Semitism complaints against Labour members is being dealt with, amid claims the process has become politicised.
In his letter to Mr Corbyn, Lord Harris said he wanted to “put on record our alarm” at the “ongoing failure” to resolve the issue.
He said the last time the Equalities and Human Rights Commission used its enforcement powers against a political party was in relation to the BNP’s “whites only” membership policy – a case that went to court in 2010.
“For the Labour Party to be in this position is nothing short of humiliating and a matter of great shame,” he said.
Lord Harris said the failure to remove anti-Semites “diminishes the moral authority of the Labour Party, undermines our whole ethos and calls into question our wider commitment to anti-racism”.
The Labour leadership has been in talks with the former cabinet minister Lord Falconer about reviewing its complaints process, including potentially the handling of historical cases.
Lord Harris said the failure to get on top of the problem was due to a lack of political leadership, rather than a lack of resources or commitment by staff.
“The failure to deal with what is now a crisis in the Labour Party is a political failure,” he wrote.
“Until the people making the decisions about discipline and expulsions accept as anti-Semitic words and actions viewed by the Jewish community as anti-Semitic, nothing will change.”
He is seeking clarification of the role played by Andrew Murray, a close aide of Mr Corbyn’s, and his daughter Laura in the complaints process.
‘No place in Labour’
And he defended Tom Watson’s right to personally intervene in the long-running row after the deputy leader was chastised by the party’s general secretary for asking for all complaints to be referred to his office for monitoring.
“Labour peers are fully behind Tom in his attempt to build confidence in the complaints system and to ensure that as a party we are operating in an accountable and transparent way.”
For Labour to use data protection as a reason for not sharing the information with Mr Watson was “not only legally questionable but laughable given the reports in the media that non-party staff closely associated with you personally have been involved in the process of looking at complaints”.
Speaking on Friday, before news of the peers’ letter emerged, Mr Corbyn said Labour would co-operate fully with the Equalities and Human Rights Commission.
He said: “We are the party that established the whole equalities law in the country and the right to investigate all organisations. We welcome it.
“We do not believe we have anything to hide. Anti-Semitism has no place whatsoever in the Labour party or the Labour movement.”