Police battling to prevent young Muslims heading to Syria to fight in the country's bitter civil war will gamble that they can persuade women in the community to inform on family members determined to head to the war zone.

Counter-terrorism officers, fearful that some of those fighting in Syria will return to Britain radicalised with the ability to carry out violent acts on British soil, hope that female family members will curb the numbers of people intent on taking up arms against the Assad regime.

Deputy assistant commissioner Helen Ball, senior national coordinator for Counter Terrorism Policing, said: "We want to ensure that people, particularly women, who are concerned about their loved ones are given enough information about what they can do to prevent this from happening. We want to increase their confidence in the police and partners to encourage them to come forward so that we can intervene and help. This is not about criminalising people. It is about preventing tragedies."

However, critics of the scheme – which is due to be unveiled formally on Thursday – said there was no evidence that women were always aware of what young people were doing. Nor was it the case that Muslim women were able or willing to inform on friends or family members.

Sajda Mughal of the Jan Trust, which aims to empower disadvantaged women and is supporting the nationwide police campaign, said: "Women are agents of change, particularly mums in the home. They are the ones who can nurture and safeguard their children."

She said concerned women unable to talk to their relatives or partners could call the police, which might lead to interventions from youth workers, not necessarily from police officers, amid concerns that turning to the authorities could lead to more British Muslims being criminalised.

At an event at the Muslim Heritage Centre in south Manchester on Thursday, police officers launched the north-west segment of the national campaign.

Appearing alongside a representative from the charity Syria Relief and workers from the government's terror prevention initiative, Prevent, chief superintendent Rebekah Sutcliffe from Greater Manchester police urged Muslim women to talk to each other if they have fears about their young people heading to Syria.

Sutcliffe said: "We are increasingly concerned about the numbers of young people who have or are intending to travel to Syria to join the conflict. We want to ensure that people, particularly women, who are concerned about their loved ones, are given enough information about what they can do to prevent this from happening."

"This is not about criminalising people - it is about preventing tragedies. We want to inform those who wish to genuinely help the Syrian cause how they can do so safely and legally."

GMP has already distributed a leaflet into communities across the north-west which aims to deter anyone thinking of travelling to Syria.

The force will be hosting a live Twitter chat on Thursday at 2pm to ask questions of a specialist Prevent co-ordinator using #askgmp or #preventtragedies.

Estimates put the number of Britons who have travelled to Syria at up to 400, with as many as 20 estimated to have 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.

Last week it emerged that 18-year-old Abdullah Deghayes, from Brighton, had died during fighting in Kassab. Abdul Waheed Majeed, 41, from Crawley, died in February when taking part in a suicide bombing mission in Aleppo.

The police campaign will operate on a national basis with regional counter-terrorism units also trying to encourage women in Muslim communities to share any concerns.

Keith Vaz. Photograph: Martin Godwin

Keith Vaz, chair of the Commons home affairs committee, whose report into counter-terrorism is out in a fortnight, said the strategy might struggle. "There is no evidence that families know. Young people are just leaving without telling families and their families are the last to know," he said. "The evidence we received is that the police don't know how to stop this."

Part of the concern in British Muslim communities stems from a mistrust of the UK authorities. Police have warned that anyone travelling to Syria should expect to be scrutinised, while the UK government has condemned the Assad regime, which is accused of atrocities.

In some parts of the Muslim community, confidence in the police is low. Martin Innes, professor of police science at Cardiff University, said older Muslim women had less trust in the police than the rest of the population. Innes, who co-authored research for the Association of Chief Police Officers in 2011 on the effectiveness of counter-radicalisation strategies, said: "People are unlikely to have proof someone is going to Syria, but have a sense of unease."

The challenge facing the UK is complex, and is not just confined to young men hoping to take up arms against forces still loyal to Assad. A handful of young women have also travelled to Syria, apparently to marry English-speaking foreign fighters. The King's College London-based International Centre for the Study of Radicalisation and Political Violence has traced four teenage girls from Portsmouth, London and Surrey who are in Syria, believed to be married to fighters, and says young girls are travelling out unaccompanied to the area, something not seen before.

In some cases information from family members has prevented people travelling to Syria, suggesting that the police appeal could be fruitful. Two 17-year-old girls were arrested at Heathrow in January en route to Istanbul, and police suspect to Syria. It is understood that the police were alerted by a family member to the girls' intentions. The girls have been released without charge.

A Syria-related terrorism trial opens next month at Kingston crown court involving Mashudur Choudhury from Portsmouth. The 30-year-old is charged with the preparation of terrorist acts under section 5 of the Terrorism Act 2006. Choudhury was arrested last year at Gatwick after arriving back in the country. He denies the charge.

The campaign will also urge people appalled by the humanitarian disaster in Syria not to travel there but instead to donate to charities working in the area.

Michelle Russell of the Charity Commission said: "There is a genuine and desperate need for humanitarian assistance to help people affected by the conflict in Syria.

"We want everyone to make informed choices about which charities to support and how to support them so that they can feel confident that their contribution really will make a difference to the humanitarian effort."

Atif Iqbal, of the United Birmingham campaign, who travelled to Syria to deliver food, said clarity was needed about how people could provide humanitarian help while staying within the law. "What is the legal framework – that is what we need some clarity on. It's very ambiguous, the goalposts keep changing," he said.

Asim Qureshi of the civil liberties group CAGE, said: "In light of the increasing hostile environment for British Muslims expressing sympathy for the plight of the Syrian people, CAGE is concerned that the police campaign has the potential to result in a McCarthyite witch hunt."

Qureshi continued: "We view this as a duplicitous attempt by the police to exploit the natural anxiety of mothers in the Muslim community to assist them in their counter-terrorism work."