ONE of the Iranian suspects held over an alleged plot to target the Israeli embassy in London may be a small boat migrant, officials believe.

Concerns that he crossed the Channel illegally before claiming asylum have stoked fears over who else may have used the route to slip into the UK.

A source told The Sun: “These claims have shocked the counter- terror team who have reported it up their chain of command.

“It has also sent shockwaves around Whitehall and those at the top of government. If proven, it just shows the problems we are facing.

“Normally a terrorist might be sent posing as a tourist with a false passport, but advances in biometrics have made that more difficult.

“The team think at least one of the group is a small boat migrant — and it could be that more than one is.

“It has long been a fear that the route from Calais and Dunkirk to here would be exploited by terrorists and criminals.

“The fact that at least one person involved in the most serious plot we’ve faced in this country for a long time might be a small boat migrant is a significant concern.”

They added: “This has come up during questioning and background checks and is extremely concerning.

“It’s particularly alarming if Iran is state-sponsoring this and if leaders there are potentially exploiting this route. This situation will increase pressure on the Government to take decisive action and resolve the issue.”

Almost 11,000 small boat migrants have arrived in the UK this year thus far, with numbers increasing despite PM Sir Keir Starmer’s promise to “dismantle the gangs.”

The suspect was among four men aged between 29 and 46 arrested last Saturday after raids in West London, Stockport, Rochdale, Manchester and Swindon.

One is said to have close ties to Iran’s government.

A fifth Iranian suspect was released on bail.

An attack was feared to be just hours away, and Special Forces were called in to help police.

The Israeli embassy in Kensington, West London, is ringed by 8ft walls, guard posts, state of the art monitoring systems and 24-hour armed security — meaning any attack would have to be huge and use lethal force.

Home Secretary Yvette Cooper has ordered security reviews in the wake of the alleged plot.

Security minister Dan Jarvis has described the arrest of the alleged plotters — and of three men suspected of spying — as “some of the largest counter-state threats and counter-terrorism actions we have seen in recent times”.

It has been reported that asylum hotels were searched as part of the operation.

Commander Dominic Murphy, Head of the Met’s Counter Terrorism Command, said the investigation was “significant and highly complex”.

Scotland Yard yesterday declined to comment on the immigration status of any of the men.

The Home Office has not commented.