The Labour activist suing the party for employing an Israeli has posted a picture of Hamas founder Sheikh Yassin with the caption “I love this man”, the JC can disclose.

Adnan Hmidan, whose legal challenge is backed by former shadow chancellor John McDonnell, has also posted selfies with Islamist figures and heaped praise on Jeremy Corbyn.

The JC’s revelations will raise serious questions about the controversial legal letter issued to the Labour Party leadership on behalf of Mr Hmidan.

Law firm Bindmans LLP wrote to the Labour Party in March on behalf of the Labour member, seeking further details about its new social media manager, who was employed in January.

The identity of the former Israeli army officer has been published on anti-Israel blogs — the JC is not disclosing it — and he has been branded a “spy” for his time in Unit 8200, the signals branch of the IDF.

Mr Hmidan works as a presenter for Alhiwar TV, a London-based Arabic language channel, the JC has learnt. Its Editor-in-Chief is Azzam Tamimi, who has been dubbed Hamas’ “special envoy” to Britain. He has said that sacrificing oneself for Palestine is a “noble cause”.

On his Facebook account, Mr Hmidan posted a series of tributes to the wheelchair-bound Hamas founder Sheikh Ahmed Yassin, who was assassinated in 2004. One of the tributes, written in Arabic, declared: “I love this man.”

A separate social media post from Mr Hmidan saluted Raed Salah, the firebrand leader of the Northern Branch of the Islamic Movement who has been dubbed the “blood libel Sheikh”.

Deported from Britain but supported by Mr Corbyn, Salah was last year sentenced by an Israeli court to 28 months in prison for incitement to violence.

Mr Hmidan’s Facebook account contains a series of selfies with controversial Muslim leaders, both at official events and in social settings. One shows the activist alongside Mohammed Sawalha, a leading figure in the Hamas network, resident in Britain. Mr Hmidan is also a committed supporter of Mr Corbyn, posting an Arabic tribute to the former Labour leader after he attended an anti-Israel demonstration.

It talked of the “significance” of Mr Corbyn’s attendance and expressed “total respect to this brave man”.

In a statement issued through Bindmans, Mr Hmidan, who has Palestinian heritage, said:

“I am very concerned that Labour has recruited a former Israeli spy to a position that involves monitoring the social media accounts of its members including those that are British Palestinian, supportive of Palestine or opposed to the occupation of Palestine.

“The party has also failed to confirm what steps, if any, have been taken to limit the risks to these members or to ensure that our data is not processed without our consent.”

Mr Hmidan said that he may refer the matter to the Information Commissioner and consider legal action on the basis of unfair and unlawful recruitment.

The Labour Party has refused to discuss what it calls a “staffing matter”. Privately, officials are said to be furious the Israeli was named in news reports on anti-Israel blogs Electronic Intifada and Middle East Eye.

Representing Mr Hmidan, Jamie Potter, a partner at Bindmans, said in a statement: “[The Labour Party] has an obligation to apply principles of fairness and natural justice to its members”.

He added: “We hope the Labour Party will now engage with our client and respond fully to questions concerning the recruitment decision.”