David Cameron is expected to address claims that three British men were tortured by police when he meets the president of the United Arab Emirates during a two-day visit to the UK.
Grant Cameron and Suneet Jeerh, both 25, and Karl Williams, 26 say they were subjected to electric shocks and beatings after being arrested for possessing drugs in Dubai in July 2012.
The three also claim they were forced to sign documents in Arabic - a language none of them understands - after having guns put to their heads.
The men, from London, were arrested while they were on holiday in the Gulf state and have been sentenced to four years in prison for the offence.
The Queen and the Duke of Edinburgh will formally greet Sheikh Khalifa bin Zayed Al Nahyan as he begins his visit later today.
The royal couple will then join the President in a state carriage procession to Windsor Castle.
Pressure group Reprieve, which campaigns on behalf of prisoners, said the men should be granted clemency and their torture allegations should be thoroughly investigated.
Reprieve investigator Kate Higham said: "The central fact of this case remains that these men were tortured by police, but there has been no proper investigation into their abuse.
"The only reasonable course of action for the UAE authorities now is to grant these men clemency, release them and allow them to return home to their families."
A spokesperson for Number 10 said: "During the state visit of His Highness Sheikh Khalifa bin Zayed Al Nahyan there will be opportunities to raise a wide range of issues including concerns about this and other consular cases."
The Sheikh will also visit Westminster Abbey with the Duke of York, where he will lay a wreath at the Grave of the Unknown Warrior. They will be given a short private tour of the Abbey by the Dean of Westminster.
The state visit will conclude at Clarence House, where the Sheikh will be received by the Prince of Wales.
He will view displays by the Prince's School of Traditional Arts and the Oxford Centre for Islamic Studies, and will have a private meeting with Charles.
The UAE has said it has investigated the allegations of torture and found them "baseless".