Unless the appeal is lodged in time for Ramadan, the Muslim fast and Moroccan "pardon" season which begins in February, Steve Bryant, who was jailed in Tangier on drugs charges, has no chance of a pardon for a further year.
Stephen Jakobi, of the organisation Fair Trials Abroad, said: "He's extremely concerned that he'll miss the deadline and be stuck there."
Bryant, from north-east London, ended his previous hunger strike last month after Moroccan authorities promised him a firm date for his final appeal within 45 days.
He is now embarked on a race against time to lodge it before Ramadan, although Mr Jakobi believes the Foreign Office is "dragging its feet", citing the example of Dutch truckers who were freed following intervention from their embassy.
Bryant's MP, Steven Norris, wrote to the British ambassador in Morocco earlier this month, urging him to add his voice to the drive for an appeal.
Mr Norris' letter states: "On 25 November at a meeting in the Moroccan embassy in London Mr Bryant's family were told that the only way Mr Bryant could be released was by a royal pardon on his behalf by members of his family and then forwarded by the Moroccan minister of justice," adding that the family was given similar advice by their MEP.
The 42-year-old father of four, who has always pleaded his innocence, is one of a growing number of lorry drivers convicted for drugs smuggling.
In March 1993, returning from his third trip to Morocco, Bryant was sentenced to 10 years imprisonment after cannabis was found in his cargo of frozen squid. He is now two and a half years into his sentence with no possibility of an early release.
His case helped prompt a joint initiative between UK customs and the United Road Transport Union. The "Memorandum of Understanding" attempts to put drivers on a par with postmen, airline pilots and ships' captains in acknowledging that not all drivers are guilty when drugs are found in their charge.Reuse content