An Indonesian court has sentenced a 56-year-old British grandmother to death for smuggling cocaine into the resort island of Bali.

Lindsay Sandiford sobbed as she heard the verdict, which stunned her defence team after the prosecution had recommended a lenient sentence of just 15 years' imprisonment.

"We found Lindsay Sandiford convincingly and legally guilty for importing narcotics... and sentenced the defendant to death," judge Amser Simanjuntak told Denpasar district court on Tuesday.

Sandiford's lawyer said it was likely an appeal would be launched against the stiff sentence, which came despite the prosecution noting she had admitted her crime and behaved politely in court.

"We object to the sentence. We never expected that our client would get the death penalty," counsel Esra Karokaro said.

"We will discuss it first with her, most likely we will appeal."

Sandiford, wearing reading glasses and with her hair pulled back, hung her head low and cried as the verdict was read out, while her sister Hillary Parson who attended the trial also sobbed.

A British embassy representative who attended the hearing declined to comment.

Sandiford was arrested at Bali's international airport in May with 4.79 kilograms of cocaine stashed in her suitcase.

Police said she was the ringleader of a drug importing ring involving three other Britons and an Indian who have also been arrested.

Sandiford argued she was forced into transporting the drugs in order to protect her children whose safety was at stake.

But the court rejected that argument and said there were "no mitigating circumstances" to allow for leniency.

"All evidence was incriminating against the defendant," said another judge on the panel, Bagus Komang Wijaya Adi.

Sandiford was arrested in May last year. ( AFP: Sonny Tumbelaka )

The court said that in fact Sandiford had not admitted her crime and that she had undermined Indonesia's hard-line stance on drugs.

"Her action was against the government's effort to combat drug use in the country and she insisted that she never committed the crime," judge Amser Simanjuntak said.

British human rights charity Reprieve said last month that Sandiford "was exploited by drug traffickers, who targeted her because of her vulnerability and her fear for the safety of her children".

Two other Britons arrested in connection with the case received light sentences last month.

Rachel Dougall was sentenced to 12 months for failing to report Sandiford's crime and Paul Beales received four years for possession of 3.6 grams of hashish but was cleared of drug trafficking.

A fourth Briton, Julian Ponder, is expected to hear his sentence at the end of this month after prosecutors recommended a seven-year jail term.

AFP