FIVE vehicles, including an ambulance, crashed on black ice after computers which monitor the temperature of the M65 failed to spot the freezing conditions.

Police said conditions on the westbound entry sliproad of the M65 at Whitebirk, were so bad ‘you couldn’t stand up’.

But bosses at the Highways Agency said their high-tech monitoring systems did not indicate that temperatures had dropped below freezing and that was why the stretch had not been treated with grit.

An investigation has been launched.

Critics said the agency had to review the way it operated following the blunder.

The ambulance was caught up in the five-vehicle pile up at 7.55am today as it was on the way to another accident caused by the ice.

Police immediately closed the stretch and called for the road to be gritted before they would re-open it.

Rush hour traffic was delayed and queues were reported on the motorway and the nearby roads.

Sergeant Ian Milnes, from the motorway police, said a car had been abandoned in icy conditions on the junction six slip road before the pile-up.

He said: “I closed the road and called immediately for a gritter.

"We are investigating why the road was in the condition that it was. You could hardly stand up on the road.”

No-one was seriously injured.

A spokesman for the Highways Agency, responsible for gritting that area of the M65, its computer sensors were ‘sophisticated’ but logged the early morning temperature at 1°C.

He said: “We are currently investigating the cause of the incident at junction 6 of the M65 and it would be premature to speculate about the cause at this time.”

County Coun David Whipp, who has been a strong critic of the gritting strategies this winter, said: “There must be a better solution where we are not just relying on computers.”

Hyndburn Council leader Peter Britcliffe said: “Whatever the glitch was it needs investigating.

"Safety can’t be left to chance.”

There were also accidents in Dunkenhalgh Way near junction seven of the M65 at Clayton-le-Moors at 8.45am and several smashes in Riley Green and Preston Old Road in Blackburn attributed to the ice.