The video evidence used this week to help reduce a £400,000 compensation claim to £2,000 could be ruled inadmissible by the introduction in October of the Human Rights Act, argues a leading lawyer.

Richard Highley, partner in solicitors Davies Arnold Cooper, warns evidence gathered by secret cameras and private detectives could be challenged in court under the Act if it was gathered in circumstances that seriously infringed the defendant's right to a private life.

The decision would be a heavy blow for insurers, who regularly use undercover surveillance to check thousands of personal injury claims a year.

Motor insurer Touchline used a secretly-filmed video tape to help reduce a £400,000 damages claim to £2,000.

Former Essex policewoman Hayley Burton, 25, had claimed she suffered severe whiplash in a road crash that left her with persistent neck pain.

She launched a £400,000 compensation claim from the other motorist's insurer.

But last week, Touchline produced a secretly shot video in court, purportedly showing Burton carrying two bags of heavy shopping from her car to her house.

Highley said the courts will face the problem of deciding where the acceptable borderlines lay when collecting surveillance evidence.

"The courts will have to decide if a person's right to privacy, which is protected by article eight of the European Convention on Human Rights, was breached in the course of gathering any surveillance evidence.

"The legal test will be whether this infringement was "just and proportionate" to the pursuit of a legitimate aim, for example detecting fraud. If the courts decide the covert surveillance was collected in a way that infringed a person's privacy, they could order it should not be shown in court and award the defendant damages."

In the Burton case, she claimed the film showed her constantly rubbing her neck and walking slowly because of her condition.

But the judge concluded there was no sign of Burton's allegedly painful condition and ordered her to meet the case's legal costs.

Burton was, however, awarded £2,000 general damages for pain and suffering she suffered immediately after the crash in 1996.