The three Britons held in Bali over an alleged cocaine smuggling plot will not face the death penalty, a major reprieve in a country with some of the world's toughest drug laws.

Indonesian prosecutors said they were seeking 12 months in prison for the three British nationals, all from Hastings and St Leonards-on-Sea in East Sussex, accused of drug offences on the resort island.

Jonathan Christopher Collyer, 38, and Lisa Ellen Stocker, 39, were arrested on February 1 after being stopped at Bali's international airport with 17 packages of cocaine that weighed nearly a kilogram, according to public court records.

They appeared in court alongside Phineas Ambrose Float, 31, who was allegedly due to receive the packages and was arrested a few days later in February.

'(Demanding the court) to sentence the defendants to one year in prison and to keep them in detention,' prosecutor Made Dipa Umbara told the district court in Bali's capital Denpasar.