Mark Lewis, the solicitor who was ordered to pay £12,500 for sending abusive social media messages to online trolls, also told a young Jewish man he hoped his father “would sit shiva for you soon”, the JC can reveal.

Mr Lewis was fined and ordered him to pay thousands in legal costs for “wishing death” on people on social media, many of whom had sent him antisemitic abuse or wished similar on him.

The decision prompted outrage in the Jewish community and several crowdfunders quickly raised the money for him.

But the JC has seen Facebook posts Mr Lewis wrote to an 18-year-old who was supporting the Labour Party during the 2017 general election campaign, telling him to “f**k off you stupid c**t”, adding that his father “should have worn a condom”.

The exchange was one of the allegations that was the subject of a formal complaint to the Solicitors Regulation Authority (SRA), which has still not published its full judgment. Offensive messages Mr Lewis sent to people who had sent him antisemitic were reported separately.

Mr Lewis claims that, while he accepted wrongdoing in actions towards the 18-year-old, his case was taken to the Solicitors Disciplinary Tribunal because he refused to do so in the second complaint relating to the trolls.

Last month the tribunal found that he had sent “offensive and profane messages”, including a number of “death-wishes”, and he was ordered to pay a fine of £2,500 and £10,000 in costs.

Mr Lewis responded by saying the SRA was “faced with a choice between Holocaust denying neo-Nazis and a Jewish lawyer… It chose to side with the neo-Nazis”.

The father of Mr Lewis’s 18-year-old victim told the JC he came forward with the details because the “record needs to be set straight”.

He said he was frustrated Mr Lewis, who made Aliyah last week, was “being treated like a hero” in the wake of the judgment because people believed he had only been abusive to neo-Nazis.

The father added: “It was inappropriate behaviour from a solicitor. It was inappropriate for an adult, especially because it was directed towards someone who was only a few days away from legally being a child.

“And also for someone who is allegedly a voice for the community – you don’t use that sort of language. It was my son, and it was abusive.

“What frustrated me is that he was being treated like a hero. I want the story to be known that he’s not a good guy and that people shouldn’t give him any money. The record needs to be set straight.”

The lawyer, who made his name representing Milly Dowler’s family against the News of the World over phone hacking, blamed his outburst on Clonazepam, a sedative he was given during a medical trial for multiple sclerosis, side effects of which include aggression and hallucinations.

Mr Lewis claimed that, after regaining full consciousness, was “was horrified to see what I had done”, and deleted the posts.

He told the JC: “I posted a horrifically horrible thing. I don’t try to excuse it all. What I said was completely wrong, it was clearly wrong. I apologise fully. I cannot say sorry enough. I deleted the posts immediately.

“Regrettably, the Neo-Nazis on Twitter had also made a complaint. I defended my actions to them as you know.

“The SRA indicated that there could be a resolution by an acceptance and apology for my actions. Whilst I accepted the wrongdoing [in the case of the Facebook comments], I explained that I would never apologise to Neo Nazis.

“If the case had just been about [the Facebook posts], it would have been resolved at that stage, without significant financial penalty or cost.

“It was the neo-Nazi issue that I objected to and refused to apologise to them. I made that clear to the SRA that I would not apologise to Neo-Nazis. It was for that reason there was a tribunal.”

Following the ruling, two separate crowdfunding pages were established to support Mr Lewis raising more than £13,000 in total – in excess of his £12,500 costs.