One of the London Bridge terror attackers was allowed to enter the UK despite Britain's intelligence agencies being told he wanted "to be a terrorist".

Youseff Zaghba was placed on an international 'watchlist' of suspected foreign fighters after the Italian police caught him trying to travel to Syria last year.

The Italians claim both MI6 and MI5 were informed of the fears surrounding Zaghba, who told police he was "going to be a terrorist" when he was stopped at Bologna airport.

But the 22-year-old Italian national was still able to enter the UK and went on to join Khuram Butt and Rachid Redouane in Saturday’s van and knife rampage in central London.

As the row threatened to overshadow  the final days of the general election, Theresa May was facing questions over the actions of the intelligence agencies and the Home Office at a time when she was Home Secretary.

During a campaign rally in Slough she announced plans to sidestep human rights laws to toughen controls on terror suspects by tightening limits on their internet use and increasing curfews

The Foreign Secretary, Boris Johnson, said the public was entitled to wonder "How on earth" the security services failed to allow Butt "through the net" after he appeared on a documentary entitled "The Jihadis Next Door" yet was still deemed low risk.

It was also revealed that Butt later received a caution for assault after attacking a man in a row over Islam.