The mother of British teenager who died under mysterious circumstances in Goa [Images] has written to Prime Minister Manmohan Singh [Images] saying she had "no faith" in Goa police, a day after her demand for a CBI probe was rejected.

"I have no faith in the leadership of the Goa police," Scarlette Keeling's mother, Fiona MacKeown, said in the letter released to the media by her lawyer.

The police initially said Keeling drowned because she was drunk, but pressure from her family forced a second autopsy that indicated she may have been raped and murdered. Chief Minister Digamber Kamat had ruled out a CBI probe.

MacKeown also accused authorities of colluding with criminals to cover up the apparent murder of her daughter.

MacKeown said she was "convinced that there is a nexus between criminal, police and politicians in the state."

"The administration tried its best to hush up the death as a simple case of drowning,'' MacKeown said. She said government officials had refused to acknowledge "the visible nexus" between drug dealers and the police.

"It was only on my request for a second autopsy that the glaring evidence of  murder and the lies of the police officers came on record," MacKeown said in the letter.

MacKeown has alleged that there are attempts to "cover up the entire incident" by showing it to be a case of drug overdose and drowning.

"Scarlette's case is being treated as (death by) drowning and the police time and again have been informing the media about the same," said MacKeown's attorney Vikram Verma reading the letter on her behalf.

"Since the same police are conducting investigations I have no faith in the police," she wrote, adding that she had full faith in India's political leadership that "the nexus" would be identified and investigated.