British agents helped the Americans seize two UK residents and incarcerate them in Guantánamo Bay where they are still detained, a former Foreign Office minister said yesterday.

Chris Mullin, a former minister for Africa, told the Guardian that as a result Britain is morally obliged to help them.

Bisher al-Rawi, an Iraqi who had lived in Britain for nearly 20 years, and his friend, Jamil el-Banna, were seized in Gambia in 2002 while on a business trip.

The British government should take responsibility for their fate, Mr Mullin said. "It may not have a legal obligation but it has a moral obligation given that we played a part in putting them into Guantánamo Bay," he said. "They will rot there until someone pulls their finger out."

Mr Rawi and Mr Banna were held by British security and intelligence officers for three days before being released, he said. The officers then tipped off the Americans about their whereabouts.

The two businessmen have always said that British agents were complicit in their abduction at Banjul, the Gambian capital. Now a former minister responsible for Africa has backed up their claims.