A Pakistani man kept in British and then American custody for a decade is suing the UK Government over allegations that he was subjected to torture, including waterboarding, by British troops.

Yunus Rahmatullah claims he was subjected to brutal treatment by British soldiers after he was captured by special forces in Iraq in 2004 before being handed to American forces shortly afterwards.

The 31-year-old, who insists he was in Iraq to set up a rice-importation business and had no links to terror groups, has launched High Court proceedings and a civil-damages claim against the Ministry of Defence (MoD) and the Foreign Office after he was released from the US-run Bagram prison in Afghanistan in May.

Download the new Independent Premium app Sharing the full story, not just the headlines

Mr Rahmatullah is believed to have been held initially at a jointly run UK/US detention facility near Baghdad airport before being transferred to the notorious American-run Abu Ghraib jail and then rendered to Afghanistan. His lawyers say that throughout his detention he had no access to legal representation and was held without charge or trial.

Papers filed at the High Court this week – after Mr Rahmatullah was able to speak to his lawyers for the first time – detail allegations that he was subjected to extreme maltreatment by his British captors, including being tied to a vehicle and dragged behind it at high speed and locked in a cage to be attacked by dogs.

In the documents, seen by The Independent, Mr Rahmatullah claimed he was tied by his arms to either side of the wall in a 1m-wide room and beaten whenever he moved his head, and doused in cold water before being left with an air-conditioning machine running at full capacity.

The Pakistani national also detailed how he had been allegedly subjected to simulated drowning. Mr Rahmatullah’s detention and transfer from British to US custody was disclosed to MPs five years after his arrest. He had no contact with his family until 2010.

In 2011, the Court of Appeal ruled that he had been unlawfully detained and granted a writ of habeas corpus. But the Supreme Court later overturned the ruling after the Government argued it had no power to demand Mr Rahmatullah’s release by the US. He is now seeking a judicial review to order a full investigation into his alleged torture and rendition alongside damages.

Kat Craig, a legal director at the charity Reprieve and Mr Rahmatullah’s lawyer, said: “Now that he has been able to speak freely to his lawyers, there is no longer any doubt that the British Government bears responsibility for his torture and illegal rendition to Bagram… The Government must now come clean about the full extent of British involvement in this disgraceful episode in our history.”

In a statement, the MoD said: “These allegations of wrongdoing by UK soldiers – which have been made 10 years after the event – are already being investigated by the [MoD’s] Iraq Historic Allegations Team. As the case is subject to ongoing legal action we are unable to comment further.”