Israeli diplomats in London issued a warning that attempts to “operate” British Jewish organisations from Jerusalem could be unlawful several months before an embassy official was caught on film talking about “taking down” MPs and setting up political groups in the UK.

In a cable to the Israeli foreign ministry, the diplomats also cautioned that operations being run by the country’s strategic affairs ministry could be dangerous and counterproductive.

“The strategic affairs ministry must understand that ‘operating’ organisations directly from Jerusalem by email and telephone isn’t good for their health,” warned the cable from London. “It’s not clear that the strategic affairs ministry understand the local law with regards to the activities of charities.”

Shai Masot, an official at the Israeli embassy in London, was caught on film boasting about setting up several political organisations in the UK, whose links to Israel he had apparently tried to obscure.

An undercover reporter with al-Jazeera’s investigations unit also filmed Masot as he and Maria Strizzolo, a UK civil servant, talked about plans to “take down” MPs he regarded as hostile to Israel, including the Foreign Office minister, Sir Alan Duncan. The Israeli ambassador to the UK, Mark Regev, subsequently apologised to Duncan and said the embassy considered the remarks “completely unacceptable”.

Masot’s business card describes him as a senior political officer, although the embassy says he is not a diplomat. He is being sent back to Israel, while Strizzolo, a manager at the Skills Funding Agency who has also worked as a Conservative party aide, resigned at the weekend.

As well as establishing what he has described as “several political support groups in the UK”, Masot has claimed credit for persuading the British government to adopt procurement guidelines that prevent local authorities and the NHS from boycotting Israeli goods.

The disclosures have angered MPs from all parties – a number of whom are demanding an inquiry – and provoked a number of former diplomats to warn that Masot would not have been operating without authority.

A British diplomat who has worked on the Israeli-Palestinian conflict said: “British parliamentarians need to feel able to criticise Israeli government policies which are illegal, such as settlements in East Jerusalem and the West Bank, without fear for their promotion prospects or being smeared as anti-Israel or even antisemitic. This is not an isolated episode. Masot is being sent home because he was caught out, not because he was a maverick.”

Israel’s strategic affairs ministry has been handed the task of countering the worldwide campaign to use boycotts, divestment and sanctions to target Israel – the so-called BDS movement. In September, the strategic affairs minister, Gilad Erdan, described the UK as the centre of the worldwide BDS campaign. Shortly afterwards, when Erdan visited London, Masot was among the Israeli officials he met.

The cable, which was first reported upon by the Israeli newspaper Haaretz, was sent from London to Jerusalem two weeks later. “Attempts to act behind our back have happened before and will happen again, but ‘operating’ Jewish organisations directly from Jerusalem, with no coordination and no consultation, is liable to be dangerous,” it said. “Operating like this could encounter opposition from the organisations themselves, given their legal status: Britain isn’t the US!”

The embassy was concerned that becoming involved with efforts to counter the BDS campaign could be incompatible with some groups’ charitable status. The cable warned strategic affairs officials “not to pose as the embassy” and added: “There’s no benefit in such operations without informing and consulting us.”

The cable was sent amid growing concern among Israel’s foreign service that the prime minister, Benjamin Netanyahu – who is also currently foreign minister – has little interest in the department.

Netanyahu’s government has declared that the BDS campaign poses a strategic threat to the country. But the strategic affairs department has been given the funds to mount initiatives to counter the campaign, at a time when the foreign ministry is facing cuts.