The brother of murdered humanitarian David Haines has warned the UK is at a radicalisation “crossroads”, with young people at particular risk of being “groomed” by extremists during lockdown.

Mike Haines, who has visited schools to discuss fighting terrorism since his aid worker brother was captured and beheaded in 2014 after being held by a four-man terrorist group of Britons dubbed “The Beatles”, described the current situation as “grave”.

Mr Haines said he was “determined to be a positive force”, despite initially seeking revenge against his younger brother’s killers.

And he said the greatest weapon people have in fighting grassroots, homegrown extremism was to “talk to young people, understand them, and don’t push them to the fringes”.

He told the PA news agency: “The situation just before lockdown was grave, and it’s only got worse.”

Speaking anecdotally, he added: “There has been more online ‘grooming’ of youths for all extremism.

“Teachers and police have told me that cases of online ‘grooming’ – and I use that word because there are so many similarities between the steps extremists take and the steps paedophiles take – have gone up.

“People are getting pushed to the fringes of society. They have a feeling that they don’t belong.

“So I believe we are now at a crossroads.”

His comments echo those of senior police officers, who warned a month into national lockdown that bored and isolated youngsters could be more susceptible to radicalisation and grooming as they spend longer online unsupervised.

Police officers also reported a “significant” drop in the number of reports being made to the anti-terror Prevent programme in the wake of school closures in March.

Mr Haines, 54, from Dundee, was speaking after legal developments last month meant the two British-raised Islamic State (IS) jihadis suspected of killing his younger brother and several other Western humanitarians edged closer to going on trial.

Alexanda Kotey and El Shafee Elsheikh, both from West London, have been in US custody for months over the deaths, including that of father-of-two Mr Haines, from Perth, who was working for an aid agency in Syria when he was captured in March 2013 before being killed on camera by the terrorists the following year.

Hate is loud but kindness is strong and deep, and it affects people in a more positive way than hatred does in a negative way.

Mohammed Emwazi – the group’s ringleader, also known as Jihadi John – was killed in a US air strike in 2015, while Aine Davis is in jail in Turkey for terror offences.

Mr Haines, who runs education charity Global Acts of Unity, said he remains hopeful that people “stand up and be a positive force” in an attempt to prevent vulnerable people from radicalisation.

He said: “The voices of hatred are loud and in all sorts of places.

“The thing that the average person in the street can do is think about how their own actions impacts on others.

“Kindness is the greatest force in this world – kindness to your neighbours, the homeless man on the street, the migrants, the people with Covid, everyone.

“Hate is loud but kindness is strong and deep, and it affects people in a more positive way than hatred does in a negative way.”

Mr Haines is due to be featured in BBC Two series In The Face Of Terror, which begins on Monday night with a focus on the so-called “Beatles” terror cell.