Merlin Entertainments faces a potential multi-million pound fine after it admitted breaking health and safety laws in relation to The Smiler rollercoaster crash that seriously injured five passengers.

Two people had their legs amputated after the collision on the ride in June last year, while three others suffered life-changing injuries.

The park’s owner Merlin Entertainments pleaded guilty to breaching health and safety laws at North Staffordshire Justice Centre.

District judge John McGarva said Merlin may have to pay a “very large fine” and sent the case to Stafford crown court for a sentencing hearing.

The firm will face an unlimited fine when it is sentenced on May 20.

One senior legal source said the penalty would run “into the millions”, depending on mitigation, the Guardian reported.

Bernard Thoroughgood, counsel for the Health and Safety Executive, which brought the prosecution, told the court that the flagship rollercoaster “was not as safe as it should have been”.

He said the ride was “mechanically sound” but there was no proper procedure in place for staff in the event of an error.

“There was an absence of a proper solid system for the staff to work on in certain situations,” he said.

Asked to enter a plea to the charge, Simon Antrobus, the barrister appearing for the firm, said: “I’m duly authorised by Merlin Attractions Limited to enter a guilty plea to the charge.”

A total of 16 people were injured when their carriage collided with an empty one on a low section of the ride.

Passengers were trapped more than 20ft from the ground at an angle of about 45 degrees before eventually being freed by emergency workers.

The Smiler reopened in March, nine months after the crash.