DEMANDS for a crackdown on homegrown extremists returning to the UK from Syria have put pressure on the Government in the wake of Wednesday's Westminster attack.

Just 54 British jihadis have been prosecuted despite an estimated 400 coming back from the war-torn region after being radicalised, according to a Mail on Sunday investigation.

Waheed Ahmed, 22, was arrested by anti-terror cops in Birmingham after he was detained on the Turkish border trying to enter Syria - but the investigation has since been dropped Credit: News Group Newspapers Ltd

Gianluca Tomaselli, 27, joined an IS sub-group called Rayat Al Tawhid, led by British jihadis in Syria but has now been spotted working in as a car park attendant in East London Credit: Times Newspapers Ltd

The report suggests the number of backtracking British extremists is likely to increase as IS continue to loose their footholds in Syria and Iraq.

Figures released last year state that of the 400 to return, only 54 individuals have been prosecuted in UK courts, with a further 30 facing charges.

Several returnees have been identified freely roaming the streets of Britain.

Gianluca Tomaselli, 27, was found to be working as a London hospital car park attendant after training to be a jihadi in Syria.

The father of two, who grew up in North London, was able to return despite links to a group that encouraged so-called “Lions” to take up arms in the Middle East.

Politics student Waheed Ahmed, 22, was arrested with nine family members in Turkey as he headed to Syria. They returned to the UK but no one was charged.

Ahmed was also arrested by anti-terror cops in Birmingham on suspicion of commission, preparation or instigation of terrorism - but the case was later dropped.

Terror group Rayat Al Tawhid supports IS in Syria and is run by radicalised Brits Credit: Video Grab

Four people were murdered in an attack outside the Houses of Parliament on Wednesday night when a terrorist launched a terrifying car and knife attack.

Khalid Masood, who was shot dead by a policeman, mounted the pavement on Westminster Bridge mowing down pedestrians before stabbing PC Keith Palmer to death at the gates of the palace.

Despite there being no suggestion Masood had travelled to Syria, the attack has reignited demands for action against homegrown terror.

Terrorism expert Professor Anthony Glees said the attack in Westminster highlights the dangers posed by 'lone wolf' extremists.

The prof, director of the Centre for Security and Intelligence Studies at the University of Buckingham, said: "These people need to be taken seriously.

While interment wouldn't be acceptable, we need to use more [Terrorism Prevention and Investigation Measures]."

This comes as news of up to 70 al-Qaeda terrorists, who were jailed in 2004-6, are due to be freed.