A police motorcyclist is today fighting for his life after a crash in Hampshire.

The officer, a man aged in his 40s, was airlifted to Southampton General Hospital following the crash with a car yesterday.

It happened on the A31 between Four Marks and Chawton.

The officerwas on duty riding along the southbound carriageway at around 1.55pm, responding to a separate single vehicle incident, which had occurred earlier on the opposite carriageway where a motorcylist was injured.

The police constable’s marked BMW motorbike was then in collision with a yellow Audi S3 car.

The officer sustained serious injuries, which were initially thought to be life-threatening.

He remains in hospital where his condition is critical but stable.

Some, but not all, of his immediate family members have been informed.

The driver of the Audi, a 40-year-old man from Four Marks, was not injured.

He was arrested at the scene on suspicion of dangerous driving.

He was questioned in custody at Basingstoke Police Station and later bailed until May 5, 2013 pending further enquiries.

Senior investigating officer Inspector Richard Parsons said: "An investigation is continuing tonight (Monday) to establish the full circumstances surrounding this collision.

“A section of the A31 has now re-opened fully after it was closed for more than six hours to allow for a forensic examination of the scene.

"We would like to thank witnesses who have given information and statements to police already.

“Although no other vehicles are thought to have been involved directly, we believe there are more motorists who would have seen the collision or both vehicles in the moments immediately before impact.

“Some of these drivers may have been commuters travelling in and out of Hampshire on Monday.

"The Roads Policing Unit will be displaying witness appeal boards at the scene of the collision this week to encourage any other members of the public with information to come forward.

"We remain in the process of contacting and informing the injured officer's immediate family tonight.

“Although his injuries are no longer believed to be life-threatening, he is in a critical but stable condition at hospital. Hampshire Constabulary is grateful for the swift and considerable assistance of other emergency services at the scene."

Anybody who witnessed the collision or either vehicle immediately beforehand is asked to contact Sergeant Darren Ord of the Roads Policing Unit at Eastleigh Police Station by phoning 101 and quoting Operation Bricklin.

Mini-com users should contact 01962 875000. Information can be given anonymously by phoning the independent Crimestoppers charity on 0800 555 111.