A security guard was crushed against a metal post and seriously injured as he tried to stop shoplifters driving off from his store.

The 33-year-old guard challenged the thieves - a man and a woman - when the alarm went off as they left the B&Q store in Chiswick High Road, west London, at around 11.45pm on Saturday.

The man threatened him with an object before the pair drove off in a Volvo estate.

A Scotland Yard spokesman said: "The couple got into the vehicle and began to drive away, while the guard and other store employees tried to prevent the car leaving by closing barriers to the car park.

"They managed to get one barrier completely closed, but the Volvo struck the other whilst the security guard was attempting to push it closed.

"The guard was crushed between the barrier, and a metal post, sustaining serious injuries - believed to his head and legs."

The guard was taken to West Middlesx Hospital and later transferred to Charing Cross Hospital, where his condition is described as stable.

The Volvo was later found abandoned in Oxford Road South in Chiswick.

The suspects were both in their mid-30s. The man was 6ft 2ins and the woman had a blonde pony-tail, and wore a white vest-top and a short pink skirt.

Investigating officer Detective Chief Iinspector Mencner of Hounslow CID said: "We urgently need to trace anyone who may have seen the Volvo being abandoned in Oxford Road South, between approximately noon and when it was found at 14.45pm on Saturday. Did you see anyone parking that car?"

Anyone who can assist should call the incident room at Feltham on 02082476329 or Crimestoppers anonymously on 0800555111.