Six passengers are said to be seriously injured after 33 passengers were rescued from the coach after it overturned on a motorway slip road.

The coach toppled over as it entered Newport Pagnell services on the M1 shortly after 4pm.

The driver of the single-decker coach was trapped behind the wheel and had to be cut free by fire crews. Passers-by and emergency workers helped rescue the passengers.

The National Express coach was on its way to Luton and Stansted airports from Birmingham.

A spokeswoman for Thames Valley Police said: "It appears that shortly after 4pm the National Express coach clipped a kerb and rolled on to its side.

"A number of passengers have been taken to hospitals in Milton Keynes, Northampton and Oxford. There are many walking wounded."

National Express said the bus left Birmingham Digbeth at 2pm and stopped at Birmingham International at 2.20pm and Coventry at 2.40pm. It was on its way to Luton Airport.

A spokesman for South Central Ambulance at the scene said 34 people had been taken off the bus.

Six were seriously injured, 11 were walking wounded and 17 were discharged at the scene.

One of the passengers said the coach was "going fast round corners" before the crash.

Kirsty Plummer, from Luton, told Sky News: "I knew something was going to happen, the driver was swerving so I put my seat belt on."

She said other passengers who did not fasten their seat belts fell on top of her as the coach overturned and were more seriously injured.

Eddie Gershon, a spokesman for Welcome Break, which operates the service station, said: "The coach went over on its side after hitting a lamp post and a tree, I've been told, and ended up in the car park.

"About a dozen staff from Newport Pagnell came out and gave initial first aid before the emergency services arrived."

A casualty bureau, for those who are concerned a relative or friend was on board, has been set up by Thames Valley Police 0800 056 0146. Police were called by service station managers just after 4pm. Four ambulances went to the scene.

In January, three people died following a crash in which a National Express coach overturned on a motorway slip road.