Police are urging motorists not to leave their cars overnight at a park-and-ride because security is "inadequate".

Following a spate of incidents in which cars have been vandalised or broken into at Thornhill, Insp Gilbert Houalla has accused Oxfordshire County Council of failing in its duty to customers by not providing 24-hour security.

The council said it intended to introduce CCTV cameras at the end of the month as part of the expansion of the park-and-ride, off the A40 at Sandhills, not as a reaction to the problems.

There are no staff at the car park from 11.30pm to 5.30am.

Cars have been broken into, stereos have been taken and windows and lights have been smashed in random attacks -- police believe the same people are responsible for all the attacks.

Insp Houalla spoke out after 15 cars were seriously damaged by vandals on Saturday at Thornhill.

"We are not just talking about stealing from cars, we are talking about wanton vandalism," he said.

"My advice to the public is do not park there overnight. It is not a safe car park."

So far this year, there have been 27 attacks on cars at the park-and-ride -- compared with just three in the same period last year.

Despite police stepping up high-profile patrols in the car park, Insp Houalla felt park-and-ride customers needed to know their cars were at risk if they left them there at night.

And he was critical of the county council.

"As it stands now, this is a 24-hour car park and the provision they have made for security is less than adequate, hence they are failing the customer," Insp Houalla said.

"We are doing our best to meet our responsibilities. But there's a limit to how much manpower we can devote to one car park when we have got several in our area.

"The end result is the customers are paying for it, which is unacceptable."

He added policing in the Thame police sector, which the Oxford park-and-ride falls into, was also being stretched.