A judge in the popular Indian resort state acquitted Samson D'Souza and Placido Carvalho in connection with the teenager's death.

The youngster's mother Fiona MacKeown indicated she planned to appeal the rulings, saying: "I am disappointed with the verdict and I will definitely move to the higher court."

The 15-year-old's bruised and half-naked body was discovered in shallow water on Anjuna beach in February 2008.

A post-mortem examination showed there was ecstasy, cocaine and LSD inside her when she was found dead.

D'Souza and Carvalho were alleged to have plied her with drugs, raped her and left her unconscious on the beach where she subsequently drowned.

They denied the charges at Goa Children's Court. 

Police initially dismissed the teenager's death as an accident.

But they opened a murder probe after Ms MacKeown pushed for a second post-mortem examination which proved the girl had been drugged and raped.

Placido Carvalho, right, arrives with his wife at the Goa State Children's Court in Panaji, India | File photo: PA Images

Ms MacKeown told Sky News the police case was "dragged out so long" and she claimed officers had lied about the "whole incident to start with".

And she believed they "tried to rubbish Scarlett and me".

She said: "It's been a parent's worst nightmare. It's bad enough to lose a child to murder without it being dragged out so long.

Before her death, Scarlett had been at a Valentine's Day party while the rest of her family had gone travelling to the neighbouring state of Karnataka.

Ms MacKeown admitted she was "very naive" and "the decision I made to let her go back to Anjuna will be a decision I regret for the rest of my life".