A woman died from carbon monoxide poisoning after British Gas engineers failed to fix her boiler - despite being called to her home 10 times.

Angela Pinkney, 35, an Oxford University admissions officer and administrator, was found dead in her bedroom in Mandlebrote Drive, Littlemore, Oxford, in March 2005.

Dc Kevin Parsons, of Oxford CID, said a British Gas engineer was arrested on suspicion of manslaughter, but was not charged due to lack of evidence.

A jury at an inquest at Oxford Coroner's Court yesterday returned a verdict of death by misadventure after hearing that engineers were called out 10 times.

The last time was the day before her death, when an engineer made an adjustment to a gas valve.

The jury heard that this adjustment caused the boiler to not work properly and there was evidence it was leaking.

Coroner Dr Richard Whittington said there was no record of any safety tests being carried out.

When Miss Pinkney developed serious symptoms, she went to Oxford's John Radcliffe Hospital. Here, away from the gas, she improved and was allowed home again, but was later found collapsed in her bedroom.

He said: "It does seem it was the adjustment or maladjustment of a valve that was crucial to how the boiler malfunction came about."

Dr Whittington said he would be writing to British Gas, and said that if a boiler was unusual, like the Powermax 155, engineers should stop work and seek advice. He said that safety tests must be carried out and records kept.

He suggested that check lists should be completed by an engineer and customers given certificates stating their boilers were safe.

British Gas spokesman Mark Duffell said the company would give the coroner's recommendations full consideration.

He said: "We would like to make it clear that all of our engineers have the most up-to-date equipment and we spend over £30m a year to ensure they are very thoroughly trained. We have strict operating procedures to very high standards and it is therefore disappointing and distressing to see that those procedures were not fully adhered to in this instance.

"We are of course conducting a full and thorough investigation into this incident."

Health and Safety inspector Mike Harrison said: "We will be considering whether there is scope for bringing criminal charges under health and safety legislation."