Roudi Chikhi had been secretly filming atrocities carried out by the Bashar al-Assad government and smuggling his footage out to al-Jazeera, YouTube and other media outlets. Then, when someone tipped off the Syrian government about his activities, he was forced to flee.

He arrived at Gatwick airport travelling on a false Canadian passport last December. The 28-year-old Kurd was then put in a police cell, taken before magistrates, convicted of travelling on false documents and given a one-year sentence. His savings of $3,500 (£2,619) were confiscated under the Proceeds of Crime Act. Campaigners claim his case is one of many where the British authorities have flouted the law that says refugees who escape from war-torn countries and travel to the UK using fake passports are innocent of crime.

Under the Geneva Convention relating to the Status of Refugees, asylum seekers have a defence for using false documents if they have no other option. Two years ago, the government admitted that almost 500 asylum seekers had been convicted of false document offences between 2009 and 2011.

Chikhi said he was shocked to find himself in Lewes prison, East Sussex. "I was with all these criminals but didn't think of myself as a criminal. There was a lot of fighting and violence and I was very scared. In Syria I was in danger, but at least I had places to hide. In prison, there was nowhere to hide."

Two months into his sentence, the Home Office granted him refugee status for five years. Yet he was left in jail to serve the four months he was required to and his savings were not returned.

"Before I came to the UK, I thought your government was so good," he says. "William Hague visited Syrian refugees in the camps in Jordan last month and was so nice to them. But here things are different. I'm an innocent person who escaped because I was exposing human rights abuses. I didn't expect to start my life in the UK with a criminal record. The government granted me refugee status very quickly yet they continued to lock me up."

The criminal cases review commission has described these cases as "a significant and potentially widespread misunderstanding or abuse of the law". It has received 70 applications for convictions to be overturned in the last 18 months. The number of cases it has referred for reconsideration by the courts has increased in recent months – in the last two years eight cases were referred but since April 2013 nine cases have been referred Lord Justice Leveson condemned four such convictions in a ruling last month, saying "a clear injustice has been done".

A spokeswoman for the UN refugees agency said: "UNHCR will closely monitor developments and would welcome the opportunity to work with the government to help ensure that people fleeing persecution are not being criminalised without having the opportunity for their asylum claim to be heard."

A Home Office spokesman said: "Our guidance clearly states that if an asylum seeker has, or may have, a defence under section 31 of the Immigration Act, then that individual should not be arrested. If a criminal investigation is launched, then any decision to prosecute rests with the CPS."

A CPS spokesperson said: "This is an issue the CPS has been working closely with our partners in the criminal justice system to address. In February this year, the CPS issued revised comprehensive guidance to prosecutors and the Home Office later issued guidance to immigration officers, reminding both that the CPS is reliant upon the Home Office for information and evidence relevant to an assessment of whether a statutory defence is available."