A policeman in charge of a child protection team has been suspended after he allegedly bombarded the 15-year-old daughter of a murder victim with raunchy emails.

Det Insp Dominic O'Brien has been suspended from duty with Sussex Police after he allegedly had an inappropriate internet chat with the schoolgirl and her mother.

Mr O'Brien won the trust of Tania Harvey, 35, while hunting the killer of her husband, Ken Harvey, 44, who was shot at the wheel of his Mercedes close to his home near Battle in 2003.

After the case the officer became friendly with Mrs Harvey and her daughter, having email and webchats with them.

Mr O'Brien, 39, is being investigated by the force's internal disciplinary department.

Mr O'Brien, who is divorced but has a girlfriend, was summoned to police headquarters in Lewes on Thursday where he was formally suspended.

He had been in charge of the Special Investigation Unit, in West Downs, which investigated child sex crimes.

His unit, which covered the towns of Worthing, Chichester, Bognor and Littlehampton, was responsible for investigating all major crimes against children, including rape and abuse.

Mr O'Brien is said to have met the teenager for the first time when he called at the family home in April, two weeks before her 15th birthday.

It is alleged that he asked Mrs Harvey for her daughter's email address, saying he wanted to send a greeting. Mr O'Brien, who has a £200,000 home in Upper Beeding, Sussex, had one internet chat with the teenager lasting an hour-and-a-half, it is alleged.

He led 100 officers in the hunt for two hitmen who raced off on a stolen motorbike after Mrs Harvey's husband was shot.

Last year career criminal Colin Meek, 35, from east London, was handed a 20-year sentence at Lewes Crown Court for the killing.

Mr Harvey, a haulage boss, has shot at point-blank range as he sat at the wheel of his car at a crossroads in the hamlet of Cripps Corner, near Battle.

The father-of-four, who lived in a £300,000 home in Broad Oak, near Hastings, was on his way to work on the morning of August 18, 2003, when he was confronted by his killers on a motorbike with the false number plate VILON. Mr Harvey, who ran a courier firm in Wadhurst, was shot five times through the car window and died two days later at Conquest Hospital in Hastings.

The court heard the motive for the shooting was a drugs deal involving cocaine worth £500,000. Mr Harvey was on bail at the time of his death, accused of importing 20kg of the drug into the UK, and had £36,000 in cash in the boot of his car.

A Sussex Police spokesman said: "We can confirm that as a result of the information we have received we have started an investigation and the officer has been suspended from duty."