A WOMAN who claimed police gave her drugs in exchange for information and triggered Britain's biggest corruption investigation, died of a heroin overdose, an inquest heard yesterday.

The claims made by drug addict Lisa Marie Davies sparked the long-running Operation Lancet inquiry, which has cost taxpayers millions of pounds.

The mother-of-two was found dead at the home she shared with her lesbian partner in February. Initially, Cleveland Police treated her death as suspicious. Two men were arrested over the supply of the drugs which killed her, but they were later released. No criminal charges followed.

Yesterday, her tearful sister, Jeanette Johnson, told of the 31-year-old's meetings with a detective who used the alias Alfie, and how she was given drugs in exchange for being a police informer.

She said: "I kept getting phone calls at my house from Alfie. He was ringing my sister for information."

Ms Johnson, who gave evidence to Lancet investigators, said the Middlesbrough detective would park his car in a lane in the Saltersgill area for meetings with Lisa.

She added: "I have been waiting for her when she has got into a car with Alfie, who has given her a bag (of heroin). She never had it when she got into the car, but she had it when she got out."

A Cleveland Police spokeswoman said: "Lancet is an ongoing inquiry and we cannot comment."

Stepmother Lynn Davies said: "We knew she was a key witness in Lancet, although we did not know a lot about this until after her death."

No criminal charges followed Operation Lancet.

The inquest, held in Middlesbrough yesterday, heard that Lisa died of "opiate toxicity" at the home she set up with her girlfriend partner in St Bernard Road, Stockton.

Home Office Pathologist Dr James Sunter said her forearms, hands and wrists had a mass of needle puncture marks, crusts, scars and track marks, all evidence of "long-standing drug abuse".

She had high levels of heroin in her blood, traces of diazepam and cocaine.

Deputy Teesside Coroner Gordon Hetherington recorded a verdict of misadventure.

Her family said afterwards they would remember her as a devoted mother to her two sons