Her family's lawyer, Vikram Varma, said the report concluded the 15-year-old died of "homicidal drowning" and not of a drug or alcohol overdose. Quoting from the report by the government's chief pathologist at Goa Medical College, Mr Varma said Scarlett died after her head was "submerged in water for five to 10 minutes".

Her death was "consistent with a picture of homicidal drowning in shallow waters", the report said. The levels of drugs and alcohol in her body were not enough to cause coma or death, it added.

Mr Varma said: "This is what we've been saying all along and what the police have been trying to cover up."

Scarlett's mother Fiona MacKeown said on Saturday she was "shocked but not surprised" at the report. She said: "I looked at her body and the bruising on her head and face and shoulder is consistent with this. She struggled, she kicked, she tried to stay alive.

"I'm just horrified that the police are still covering up my daughter's death. Who are they covering for? It must be someone very important."

Scarlett, on holiday in Anjuna beach from her home near Bideford, north Devon, was found on February 19 semi-naked, raped and murdered.

Local police initially said the death of Scarlett was an accidental drowning. A murder investigation was launched following a second post-mortem examination - carried out following pressure from Mrs MacKeown - which showed she had been attacked.

Already in custody is Placido Carvalho, aged between 30 and 35 years old, who has appeared in court on suspicion of drugging the girl and assisting in the murder by that act. The first man they arrested, Samson D'Souza, 28, was remanded in custody on suspicion of rape.

Scarlett's Indian boyfriend has criticised Mrs MacKeown for failing to protect her daughter in the weeks leading up to her death. Speaking to the Mail on Sunday in his first interview, Julio Lobo, 25, claimed Mrs MacKeown left Scarlett for about three weeks without money while she went on holiday, and knew she had a heavy drinking habit.