Labour’s investigation into a prominent internal critic of Jeremy Corbyn’s leadership has been branded “a farce and a disgrace” by the MP’s lawyers.

Solicitors acting for Ian Austin wrote to party general secretary Jennie Formby to complain that, three weeks after being told he was under investigation, the Dudley MP had still not been given details of the allegations against him.

Accusing Labour of “failing to observe the most rudimentary principles of natural justice, due process and transparency”, solicitors Hamlins wrote: “This process has been a farce and a disgrace. It has plainly been designed to silence our client for his legitimate, honestly held criticisms of Mr Corbyn’s failure to address the scourge of anti-Semitism in the Labour Party.”

The letter emerged as a second MP subjected to disciplinary proceedings after criticising Mr Corbyn attacked the party leadership’s “bullying” approach.

Dame Margaret Hodge said she was in “no doubt” figures at the top of the party want to purge opponents of the leader.

Anti-semitism in LabourLabour dropped its investigation into allegations against Dame Margaret Hodge (Yui Mok/PA)

A probe into the former minister, launched after she confronted Mr Corbyn over his handling of anti-Semitism complaints, was dropped by the party on Monday. She denied having offered an apology to settle the matter and called for the inquiry into Mr Austin to also be halted.

In an interview with the Evening Standard, Barking MP Dame Margaret – who is herself Jewish and lost relatives in the Holocaust – said the Labour Party had become a “hostile environment for Jews”.

Asked if she believed there was a “purge” of Mr Corbyn’s critics under way, she replied: “I have absolutely no doubt that there are those in the leadership who want to get rid, whether it is through deselection or disciplinary action, of any opposition.

“The new style of politics is bullying and intolerance, not gentle and inclusive.”

The Hamlins letter, dated August 1 and published on Tuesday on Mr Austin’s Twitter feed, said that the Dudley MP, whose adoptive father was a Jewish refugee from the Nazis, had been subjected to a “Kafkaesque” disciplinary process.

A letter on July 19 informing him that he was under investigation for “abusive conduct” in Parliament, gave no details of the alleged incident, but “senior party sources” were quoted in the press claiming that he had intimidated party chairman Ian Lavery.

In a July 24 meeting with chief whip Nick Brown, he was told that complaints had been made by Mr Lavery and left-wing MP Chris Williamson.

A letter from Mr Brown two days later said there had been complaints that he “approached other MPs unasked and asserted your point of view in a loud and aggressive manner, thereby creating an incident”.

Mr Brown also said there had been “other incidents of a similar nature”. He formally warned Mr Austin against “any repeat of such behaviour” and issued a reprimand for what he said were “a number of complaints”.

Hamlins said it was “completely inappropriate and contrary to the rules of natural justice” for Mr Austin to have been issued with a warning and reprimand without being given details of the allegations against him or an opportunity to defend himself.

The lawyers demanded immediate details of the substance of complaints and the identity of the person conducting any investigation, as well as an assurance that the probe would not be led by anyone from Mr Corbyn’s office.

Asked for the party’s response, a Labour spokesman told the Press Association: “This is an ongoing investigation. We don’t comment on ongoing investigations.”

The inquiry into Dame Margaret came after a heated exchange last month in which she was said to have called Mr Corbyn an “anti-Semite” and a “racist” over his refusal to adopt in full the International Holocaust Remembrance Alliance’s (IHRA) definition of anti-Semitism.

Journalists were briefed that the decision to drop the inquiry had been taken after she expressed “regret” to Labour chief whip Nick Brown for the way she had raised her views.

But the MP swiftly hit back through her lawyers Mishcon de Reya, who said the move was a “cynical attempt to save face in your necessary climbdown”.

In a letter, they said it was over two weeks since Dame Margaret had spoken to Mr Brown about the matter and that they had had no further discussions since.

“She did not express regret – in those or any other words,” the letter said.

“As you are aware, our client will not apologise for her conduct and words, as she did nothing wrong.

“You have entirely misrepresented our client’s discussions with the opposition chief whip in a cynical attempt to save face in your necessary climbdown.”