THE UK authorities have been accused of "monumental incompetence" over their handling of children and young people at risk of being radicalised online.

Scottish solicitor Aamer Anwar claimed security officials knew that one of three missing schoolgirls had contacted Glaswegian jihadi bride Aqsa Mahmood online but failed to notify the girls' families.

The lawyer, who represents Miss Mahmood's family, warned that radicalisation needs to be treated as a child protection issue and said parents should be notified as soon as police have any information that their child may be at risk.

His comments came as the families of the three missing London teenagers, Shamima Begum, 15, Kadiza Sultana, 16, and Amira Abase, 15, pleaded for them to return home.

The girls - believed to be on their way to Syria after boarding a flight to Turkey on Tuesday - are understood to have been recruited by Miss Mahmood online after one of them sent her a message.

Mr Anwar, who has called for an inquiry into what happened, said: "We know from the police that they regularly monitor Aqsa's online accounts so they would have been well aware of this contact.

"The fact that they didn't contact the girl's family to let them know suggests that either there has been monumental incompetence on the part of the security services or they simply don't give a damn.

"If a child went missing and it turned out the police were aware that she had been contacted by a known paedophile but had not told the parents, there would be a public outcry. This case is just like that, this is child abuse.

"These are 15-year-old girls we're talking about and what will happen to them is that they will not be allowed to leave once they meet up with Isis.

"They will have their passports torn up and they will be required to marry an Isis jihadi. Why is it that this isn't being treated as a child protection issue?"

The solicitor added that the girl who contacted Miss Mahmood should have been placed on a "watch list" which means she would have been returned to the country from Turkey.

He also questioned why the three girls were not stopped by airport security before boarding the Turkish Airlines flight at Gatwick.

"Here we have two 15-year-old girls and a 16-year-old, dressed conservatively and wearing the Hijab, travelling to Turkey alone without their parents", he said.

"Surely this should have raised alarm bells?"

He added: "I'm calling for an inquiry into this. The families of Aqsa and these three girls have a right to know exactly what the security services knew and what lessons can be learned for the future to stop young people going off to join Isis."

Meanwhile, the families of the missing schoolgirls have appealed for them to stay out of Syria and return home.

Miss Begum's family issued a statement saying they miss her "terribly" and are "extremely worried" about her.

They said: "Please, if you hear this message, get in touch and let us know you are safe. We want you home with us. You belong at home with us.

"Syria is a dangerous place and we don't want you to go there. Get in touch with the police and they will help to bring you home. You are not in any trouble."

Miss Sultana's family described the situation as a "complete nightmare", adding that they are praying for her safe return.

The family of Miss Abase said: "You are strong, smart, beautiful and we are hoping you will make the right decision. You had bright future, so please return home."

It has emerged that the girls were questioned as part of a "routine inquiry" by the Metropolitan Police just two months ago after one of their classmates, also 15, travelled to Syria.

However, it was only when their families raised the alarm that authorities discovered the girls had fled the country.

Scotland Yard said there was "nothing to suggest at the time" that the trio were at risk and their disappearance has "come as a great surprise, not least to their own families".

The issue had prompted former coalition minister Baroness Warsi to warn that people are increasingly being "radicalised in their bedrooms", adding that blaming mosques is an "easy answer".

Former foreign secretary William Hague also said it is "unrealistic" to expect the security services to find "every single thing", saying: "You are looking for needles in haystacks."

Scotland Yard refused to respond to Mr Anwar's criticism.