Foreign Islamic State fighters held in overcrowded prisons and lawless refugee camps in north-east Syria – including about 60 Britons – should be put on trial there as part of an international effort to de-radicalise the region, according to senior local officials.

Politicians and soldiers from the Kurdish-led region said they needed western help to deal with the prisoners locally, including setting up a recognised war crimes tribunal, amid warnings that Isis could otherwise rebuild.

Images emerged this week of the insanitary conditions in makeshift prisons where people of more than 50 nationalities were held in packed cells, sometimes 20 to a room. Meanwhile, local politicians admitted they had lost control of the refugee camps to Isis radicals.

Dr Abdulkarim Omar, the de facto foreign secretary of the self-styled Autonomous Administration of North and East Syria, and the co-chair of its foreign affairs committee, said: “We call for the establishment of an international tribunal to prosecute those fighters here in our region.

“Those people, the Isis criminals, committed their crimes in our region and against our communities. Evidence, proof and witnesses against them are in this region, and we can prosecute them.”

Omar, speaking before pictures of the prison interiors were published in the Times, admitted his administration was struggling with the postwar legacy. Omar said the region only received “5% of the resources it needs” from the international community to help. Officials repeatedly described the prisons and camps as a “ticking time bomb”.

Estimates of the number of Isis fighters in detention vary. The administration puts the figure at 6,000, including 1,000 foreigners, but others say the true number is double that. Some have been in custody for two or more years without trial after Isis sustained a series of battlefield defeats.

Refugee camps hold in excess of 100,000 people, mostly women and children, with the largest, the al-Hawl camp, holding more than 70,000.

Inside al-Hawl camp, the incubator for Islamic State's resurgence Read more

Isis lost the last of its territory in March, defeated by the primarily Kurdish members of the Syrian Democratic Force (SDF) with military support from a US-led coalition, marking the end of an eight-year war that killed 12,000 troops. What was initially a Kurdish territory on the Turkish border has become a multi-ethnic region of 5 million people, east of the Euphrates River, and separate from the areas controlled by President Bashar al-Assad.

British sources estimate that just over 60 adult Britons – an equal mix of men and women – are being held in detention or are living in camps in north-east Syria. The UK has made little effort to repatriate them.

In two high-profile cases, the UK has stripped citizenship from Shamima Begum and Jack Letts. Two others accused of murdering western hostages – Alexanda Kotey and El Shafee Elsheikh – may be extradited to the US.

Map of Syria Map of Syria

Two British MPs who went on a fact-finding mission to north-east Syria last month, including a visit to a refugee camp, said the UK had a “debt of honour” to help those who fought Isis on the ground, and said the situation in the prisons and camps was critical.

Lloyd Russell-Moyle, a Labour MP who chairs the parliamentary group on north-east Syria, said the local authorities needed western help: “The time bomb of captured Isis fighters and radicalised families is beyond the capacity of north-east Syria to address. Failure to prioritise this would be international security negligence of the first order.”

The MPs also criticised the UK for not recognising north-east Syria politically, with ministers refusing to meet administration officials when they visited London earlier this year.

Another member of the delegation, the Conservative MP and former prisons minister Crispin Blunt, said: “So far the shirking of our nation’s responsibility has been wholly shameful.” He called on Boris Johnson to “reverse this position with due urgency”.

The lack of local control has prompted concerns that there could be a repeat of what happened in Iraq in the aftermath of the US invasion, where Isis leaders congregated in, and were further radicalised at Camp Bucca. Last month, Isis’s leader, Abu Bakr al-Baghdadi, released an audio message calling on Isis fighters to liberate prisoners and those living in refugee camps.

The US, which has 1,000 troops in the region, is opposed to the creation of a local war crime tribunal. It wants foreign fighters to be repatriated and put on trial in their home countries.

Whitehall sources argue that problems with collecting evidence that could stand up in a British court mean it may only be possible to charge returnees with membership of a banned organisation, which carries a maximum 10-year sentence.

Control of refugee camps, such as al-Hawl, is increasingly in the hands of “radical women” from Tunisia, Somalia and Russia. On their recent visit, the MPs heard aid workers report that their tents were burned down and they are regularly pelted with stones.

Sixteen British families are among the 12,700 people from outside Syria and Iraq living in al-Hawl, according to the local administration, though there is limited evidence that any sustained effort has been made to establish details about who is in the camp. “They haven’t done any fingerprinting or any ID,” one of the British politicians said.

Conservative dress codes were strictly enforced. Members of the SDF guarding the camp said a mother killed her daughter with a hammer for not wearing the chador and her body was left out in the camp as a warning to others.

Local politicians said the UK and other countries should be prepared to repatriate children born to Isis members, as part of a deradicalisation programme. “These children are victims, their only guilt is that they belong to parents who joined Isis,” Omar said.

Describing the children in the camp, who are from 55 countries beyond Syria and Iraq, as “the cubs of the caliphate”, Omar said: “If we do not address this problem and provide rehabilitation for some of them, we expect a future of terrorists.”

Some countries, such as France and Belgium, have taken in a few orphaned children, but a recent review led by the Home Office concluded that children in Syria with a claim to British citizenship should be left there.

Over the weekend, however, it was reported that Johnson was considering whether to authorise a raid by UK special forces to repatriate children born to British parents.