The women - four teenagers and a 26-year-old - were killed as they travelled from the country's capital, Quito, to a fishing village on the coast as part of a trip organised by gap year travel specialists VentureCo.

Ecuadorian police said a lorry carrying a load of sand crashed into the left side of the bus. The lorry driver fled the scene.

A further 12 Britons, a French national and two Ecuadorians, a driver and a tour guide, were also injured in the accident.

The Foreign and Commonwealth Office said (FCO) it was understood the local authorities had appointed a prosecutor to investigate the tragedy.

The victims were named as Rebecca Logie, 19, Indira Swann, 18, Elizabeth Pincock, 19, Emily Sadler, 19 - all students taking a year out between school and university - and Sarah Howard, 26, a freelance trip leader on her first expedition for VentureCo.

Gordon Brown expressed his sadness at the tragic news. His spokesman said: "The Prime Minister was deeply saddened to hear of the deaths of five young British people in Ecuador. His thoughts are with their families and friends."

Mark Davison, the director of VentureCo, which is based in Warwick, said the group were reaching the end of an eight-hour journey and were just 30 minutes from their destination when the accident happened.

The group were taking part in the 15-week "Inca and Amazon Venture", which set out on March 27 and began with two weeks of Spanish language tuition in Quito.

Mr Davison said the risk assessment for the trip had identified the high Andes, where the land frequently drops away dizzyingly from the roads, as the most dangerous areas for road travel, and an accident in the coastal area was unusual.