A government campaign to urge Muslim women in Britain to tell the police if they suspect their sons are planning to travel to Syria to fight or help the war effort has been widely criticised for targeting the wrong people.

A nationwide appeal was launched on Thursday by counter-terrorism officers hoping to curb the numbers of people intent on taking up arms against the Assad regime, who they fear may return radicalised to the UK.

At a briefing at the British Muslim Heritage Centre in Manchester, officers urged mothers to check their sons’ Facebook pages and monitor their internet use to see what they were watching on YouTube and who they were interacting with.

“It’s a bit like when I saw that there was a lot of talk on my son’s Facebook about Neknominations [a game where young people film themselves downing drinks before nominating others] – we had a chat about why getting involved in that sort of thing was not sensible,” said Inspector Andrea Bradbury from Lancashire constabulary.

“I’ve spoken to young people who have been out to Syria who say they they’d seen videos on YouTube with young people waving guns and thought it looked exciting. One even said he thought it would be like on the war games he played on his games console. Of course a real war is nothing like a video game.”

But the initiative was soon criticised as unworkable, with some Muslims warning that no one would report their loved ones to the police for fear of criminalising them. The aunt of Abdullah Deghayes, an 18-year-old man from Brighton killed in a gunfight in Kassab, Latakia province, earlier this month, said she had not heard anything helpful or useful in the announcement.

Amina Deghayes warned that families were already urging their loved ones not to fight in the country, but too often their appeals fall on closed ears. She said: “If the steps are to speak to the guys before they leave, I think people already have – they do not need the government to tell them that.

“In the case of my nephew, he ran away. At what point would we speak to him? I am not being negative. Maybe the actual details of the proposals are more useful than that, but at the moment I haven’t heard anything helpful or useful – it would be better than criminalising them, which is the only thing that is going on.”

Abdullah Deghayes died in a gunfight in Latakia province earlier this month. Photograph: PA

In February Abdul Waheed Majeed, 41, from Crawley, West Sussex, became the first Briton believed to have carried out a suicide bomb attack in Syria. On Thursday, Arif Syed, a community leader in Crawley, dismissed the police appeal. “I don’t think it’s going to be effective,” he said. “In the case of Majeed, his wife, his mother told him not to go, his sister told him to not to go and he didn’t take any notice of them. People will do what they want to do.

“This is a very complicated issue and this government is running out of ideas. There has been a lot of talk and nothing credible is coming out of it. I think it’s scaremongering. It’s not individual freedom fighters travelling from the UK that will make any difference; they will only lose their lives.”

Deghayes fears the threat of prison for those returning from Syria is counterproductive and could lead to British fighters staying there for longer, saying: “Even if one of them was to consider coming back, they will have to think: ‘Am I going to prison?’ Fair enough, that may be a consequence of their actions but we have to think of the implications. They are not middle-class thinkers and always thinking of all the possible consequences.

“What can they do? Even if they do change their minds, they are caught between a rock and a hard place. If they come back, they may end up in prison. If they do not, they have to stay there.”

But in London, the Metropolitan police’s deputy assistant commissioner Helen Ball, senior national co-ordinator for counter-terrorism policing, said any Briton fighting, or training to fight, in Syria should expect to be investigated on their return.

Ball said: “Women might see their family members spending more time on the internet, they might get very angry about what’s going on in Syria … If they see those sort of signs … then we hope they will come forward to the police, or partner organisations or community members.”

She said the information would not be shared with the security services, MI5 and MI6, and that the threat from Britons going to Syria was her main concern.

“This is not about criminalising people,” she said. “It is about preventing tragedies.

“We want to increase their confidence in the police and partners to encourage them to come forward so that we can intervene and help.”

Ball said the “red line” that would trigger counter-terrorism investigations would be fighting with any group in Syria, including those with tacit western support.

“Fighting full stop and training to fight is likely to lead to a police investigation,” she said.

Ball said British Muslims were driven by different motives to travel to Syria: “Some of them with absolutely strong ideological motives to support the suffering of the Syrian people. Some of them wanting to fight.

“I have seen the effect on families who have lost them, and how torn apart they are by losing them.

“We are starting to think how women in particular can challenge the attitudes of people themselves, and stop their young people putting themselves in dangerous positions and possibly becoming radicalised.”

Some in British Muslim communities distrust the motives of the police and government. They believe previous programmes, such as Prevent, turned into “spying programmes” gathering intelligence on the innocent.

On Thursday morning Scotland Yard officers met some Muslim women’s groups that support the campaign.

Ms Tufail, from Greater Manchester police’s prevent team, which aims to tackle the problem of terrorism at its roots in communities, urged anyone concerned to trust the police. “This is not about putting someone on a list. It’s about safeguarding and supporting them.”

The House of Commons home affairs select committee chairman, Keith Vaz, also questioned the national appeal, warning that it was unlikely parents would report suspicions about their children to the authorities. “All the evidence indicates that the families themselves are the last to know. They are also most unlikely to tell the police. The police are not the Samaritans, they are the first step in the criminal enforcement process.

“This needs to be addressed at a peer group level, include partnerships with social media and have the full engagement of the communities affected. They hold the key. Young people need to be persuaded that if they go to Syria they may end up dead.”

Estimates put the number of Britons who have travelled to Syria at up to 400, with as many as 20 having been killed. Police say so far this year the number of “Syria-related arrests” has increased substantially, to 40 between January and March, compared with 25 people in the whole of 2013.

Four people have recently been arrested in Greater Manchester on suspicion of terrorism charges relating to Syria. In March, Jamshed Javeed, a 29-year-old science teacher from the Levenshulme area, was charged with supporting terrorism – an offence that can involve fundraising for a terrorist organisation or supporting a terrorist group in other ways.

Three others were arrested by GMP on 11 March, suspected of being involved in travelling to or supporting fighting in war zones, but were released without charge a few days later.

• This article was amended on 24 July 2019 to remove some personal information.