Briton Lindsay Sandiford (right) listens to her translator during her trial in Denpasar, on the Indonesian resort island of Bali.

Denpasar, Indonesia -

Britain has raised claims that Indonesian authorities mistreated a British grandmother on death row for drug trafficking, in a statement supporting her appeal which was seen on Wednesday.

The Foreign and Commonwealth Office submitted a document in Indonesian to the Denpasar District Court citing allegations that officials had “violated Lindsay Sandiford's fundamental rights under international laws and the Indonesian constitution”.

They said Sandiford, 56, was allegedly threatened with a gun and deprived of sleep.

“The British government wants to attract the court's attention to serious allegations of mistreatment by related officers and officials at the time Lindsay Sandiford was first detained,” said the document obtained by AFP from the court.

The document reminded the Indonesian government it had ratified the UN Convention Against Torture which outlaws forced sleep deprivation.

It also said Sandiford's crime was “not exceptional enough” to warrant capital punishment and mitigating factors, such as her cooperation with police, should be taken into account in her appeal.

The unusual intervention comes after the High Court in London dismissed Sandiford's request for financial help in appointing a lawyer, estimated by the NGO Reprieve to cost 2 500 pounds ($1 134).

Sandiford was sentenced to death on January 22 for smuggling nearly five kilos of cocaine worth $2.4 million into Bali in May, even though prosecutors recommended a 15-year jail term.

She lodged an appeal against her death sentence on Monday, when the British government statement was submitted as an “amicus curiae” (friend of the court), - a party that offers unsolicited information in a case.

During her trial Sandiford argued she was forced into transporting the drugs to protect her children, whose safety was at stake. The court rejected her claims, saying she had damaged the island's reputation as a tourism destination. - Sapa-AFP