An investigation into three brothers who left Brighton to fight in Syria has uncovered a further 25 jihadists in the south coast town.

Court orders have prevented a further three from travelling to join jihadist groups, but counter-terrorism officials warn the group may plot to kill at home in a Lee-Rigby style attack.

The sea-side party-town of Brighton on the south coast of England is best known for being the gay capital of Britain, and home to one of the largest LGBT populations in the country.

But a secret investigation by Brighton and Hove council officials and counter-terrorism experts carried out two years ago uncovered a hotbed of jihadist activity, which officials feared may lead to vigilante attacks on the streets of Brighton, The Sunday Times has reported.

Despite the fears, it appears that no arrests have been made.

In October 2013 three brothers, Amer, 22, Abdullah, 18, and Jaffar Deghayes, 17, left their family home to join Jabhat al-Nusra, an offshoot of al-Qaeda operating in Syria. Two other men, including their childhood friend Ibrahim Kamara, 19 later fled to join them.

Apparently prompted by their departure to investigate, by March 2014, council and counter-terrorism officers had identified 28 aspiring jihadis in the town, including the five who had already travelled abroad.

Half of those identified were teenagers, while 60 percent were said to be converts to Islam.

“It’s obviously a serious concern that there are 28 young people brainwashed to the point that they want to join jihadist groups or consider plotting against innocent people here at home,” said a source.

“The concern has not abated; there’s a lot of extremism-related problems lurking that the police and social services are attempting to deal with.”

Three of the would-be jihadists, including one girl, were placed under court orders to stop them heading to Syria. But officers said the group were planning terrorist activities nonetheless, hoping to carry out small-scale attacks using pistols or knives.

“The first threat level that they were concerned about is that some of them would take a knife and kill people, a bit like what happened in the Lee Rigby attack,” said a source.

Attacks using explosives were ruled out as a potential threat as it was deemed unlikely that young people could access the materials needed to make them.

The source added that the list of 28 people was well known to council and intelligence officers, and were judged to be at “risk of travelling to Syria”. At least one of the teenaged girls has been referred to the government’s counter-radicalisation program ‘Channel’.

A redacted report into the investigation is due to be published shortly. However, officials are already due to reveal that both the police and social services, run by the Green-party led council at the time, missed a number of opportunities to prevent the Deghayes brothers from becoming radicalised over a five year period.

Jaffar Deghayes was killed in Syria in October 2014; shortly after his death his sister Aîóshà published a tribute on Facebook, describing him as “an honourable man helping fight an oppressive tyrant,” and saying she hoped to be reunited in Paradise with him and their brother Abdullah, who had died fighting in Syria six months earlier.

The boys are nephews of Libyan-born Omar Deghayes, who was held at Guantanamo Bay for five years before being released without charge. He was later awarded a sizeable sum in compensation by the British government for his detention.