Labour is clamping down on former staff blowing the whistle on its handling of anti-Semitism allegations ahead of a BBC documentary, it has been reported.

The Sunday Times says up to half a dozen ex-employees have torn up non-disclosure agreements (NDAs) to speak to the Panorama programme, which is due to be aired on Wednesday.

According to the paper, Carter Ruck – acting on behalf of Labour – have written to Sam Matthews, the party’s former head of disputes, warning he could face legal action for breaking his NDA.

A letter is reported to warn that the party “cannot be expected to and will not tolerate its former employees wantonly disregarding their obligations by selectively leaking information to the media”.

Another former aide also received warnings last year from a different law firm representing Labour, the paper said.

Former Labour MP Luciana Berger, who resigned from the party over anti-Semitism, said on Twitter: “Every day I think that @UKLabour can’t possibly sink to a deeper low. And yet they manage it.”

“This from a party whose leadership have vociferously supported whistleblowers and championed whistleblowing policies,” she added.

“They just don’t want it to apply to themselves.”

The BBC documentary, entitled Is Labour Anti-Semitic?, will see reporter John Ware explore the ongoing anti-Semitism row, and will feature interviews from “key insiders”, according to the programme synopsis.

A Labour source accused the BBC of creating a “one-sided narrative” and said it would be complaining to the director-general, telling the paper: “With a possible general election around the corner, this smacks of bias and interference in the political process by the BBC and a clear breach of their own editorial guidelines.”

A Labour spokesman told the Sunday Times that those involved in Panorama were “disaffected former officials including those who have always opposed Jeremy Corbyn’s leadership, worked to actively undermine it, and have both personal and political axes to grind. This throws into doubt their credibility as sources.”

Wes Streeting, Labour’s MP for Ilford North, said he would “whistleblow in (the) House of Commons for anyone who needs me to do so”.

Writing on Twitter, he said: “Labour opposes NDAs yet seems to impose them. I’m protected by Parliamentary privilege. I’ll whistleblow in House of Commons for anyone who needs me to do so. Sunlight is the best disinfectant. No more excuses or hiding places. You should promise the same @jeremycorbyn.”

Chairman of the Jewish Labour Movement Mike Katz said: “Given Labour has called for scrapping of NDAs & greater legal protection for whistleblowers, it’s both hypocritical and just plain wrong of it to set expensive lawyers on former staff who are acting in the public interest to shine a light on institutional anti-Jewish racism.”

And Mike Gapes, who quit Labour earlier this year in protest at Jeremy Corbyn’s leadership, tweeted: “I hope that my former PLP (parliamentary Labour party) colleagues are pleased that their £156 a month special contributions to the Party are being well spent on expensive lawyers Carter Ruck and on attempting to silence former Labour employee whistleblowers.”