Labour is facing fresh demands to set up an entirely independent system for overseeing antisemitism complaints, as the party braces for more revelations about its handling of the problem.

As it emerged that the lawyer appointed to advise the party on disciplinary issues just a year ago is quitting his post, Margaret Hodge, the Labour MP who has led criticisms of mishandling of antisemitism among members, said the party should not replace him. Instead, she said Labour should use the opportunity to set up a completely independent system.

“We’ve been saying for some time that we have got to have an independent system,” said Hodge, after it emerged that Gordon Nardell QC, who was appointed last June as the party’s first in-house counsel dealing with disciplinary matters, would return to his chambers in August. The announcement was made quietly by his chambers after multiple Labour sources said that he had decided to leave.

Hodge added: “Replacing him is no good, because you end up with the system being corrupted by political interference. If he has gone, we should get on and establish a totally independent system that cannot be politicised by anyone. If you want to start re-establishing trust, that is the only way to do it.”

The BBC is planning to broadcast an investigation this week which Labour sources said was likely to reopen claims, denied by the leadership, that there was political interference in how some cases were handled. Labour is already being investigated by the Equality and Human Rights Commission and any new evidence could form part of its inquiry.

Former prime minister Gordon Brown will today call on the party to finally eliminate antisemitism from its ranks. He will say there is a fight on for the “moral soul” of Labour. “To fail to act against the abuses we have witnessed runs counter to the very principles of the Labour Party we joined,” he is expected to say.

In March, the Observer published details of internal emails that suggested members of Labour’s high command opposed recommendations to suspend several party activists accused of antisemitism. The correspondence, dating from March to May last year, covered a period immediately after Corbyn had vowed to be a “militant opponent of antisemitism” and to have “zero tolerance for antisemites”.

The party denied any claims of political interference in the process.

A Labour spokesman said this weekend that the party was “fully committed to the support, defence and celebration of the Jewish community and implacably opposed to antisemitism in any form”.