Supermarket bosses have lost a Supreme Court responsibility fight after a member of staff assaulted a motorist at one of their petrol stations - and legal experts say the ruling will have implications.

Ahmed Mohamud - who was assaulted in Small Heath, Birmingham, in 2008 - argued that Morrisons should be held responsible for the actions of an employee.

Morrisons disputed the claim - and won fights in lower courts, including the Court of Appeal.

But the Supreme Court has ruled against Morrisons.

A panel of five Supreme Court justices analysed evidence at a hearing in London in October and delivered a ruling on Wednesday.

Mr Mohamud had died following the launch of the litigation - a relative had continued the claim.

Justices heard that Mr Mohamud had asked kiosk assistant Amjid Khan if it was possible to print documents he had on a USB stick.

Mr Khan was abusive, used racist language and then followed Mr Mohamud on to the station forecourt and punched and kicked him.

Mr Mohamud argued that the assistant should be regarded as ''wearing the badge'' of Morrisons and ''representing its brand standards''.

Supreme Court justices agreed.

They said it was wrong to "to regard Mr Khan as having metaphorically taken off his uniform the moment he stepped out from behind the counter".

And they said when Khan followed Mr Mohamud to his car and told him "not to come back to the petrol station" he had been giving an "order" and "purporting to act about his employer's business".

Specialist employment lawyers said the ruling was significant.

Nicholas Le Riche, a partner at law firm Bircham Dyson Bell, said: "Employers should be warned that this decision has potentially widened the scope by which organisations can be responsible for their employees' actions."

Adam Grant, a partner at law firm Wedlake Bell, said the ruling meant that the actions of employees in customer facing roles could expose employers to increased financial risk

Tom Stenner-Evans, who is based at law firm Michelmores, added: "Although the underlying legal test remains the same, this decision arguably broadens the range of circumstances in which employers might be vicariously liable for the actions of their employees.

Martin Pratt, a partner at law firm Gordon Dadds, went on: "The Supreme Court has massively increased employers' potential liability for their employees' actions. Previously, if an employee did something outside the scope of their employment tasks then the employer would not be liable. So, before today, an employer would only have been liable for an assault like the one in this case if it were done while the employee was doing a task as part of his employment - an overly aggressive nightclub bouncer for example.

"This case changes all that completely. Now employers can be held liable for criminal acts performed by their employees at work even when those acts were personal acts not directly connected to their employment. Unlike a bouncer violently restraining an unruly customer, the assault by the forecourt worker could not be said to be related to his employment tasks in any way, but the Supreme Court held Morrisons to be liable nonetheless."

A spokesman for Morrisons said damages had been agreed and would be paid to Mr Mohamud's family.

"When this appalling incident happened, we were horrified and dismissed Amjid Khan," said the spokesman.

"We then offered a settlement option to Mr Mohamud but he and his legal team wanted to progress a case which involved widening the rules on vicarious liability."