Britain's top judge has attacked a sentence handed down to an armed robber as lenient – but has refused to increase it.

Neil Gordon was given a community order after stabbing and slashing a lone shopkeeper, sparking outrage from his victim, who condemned the punishment as "a joke".

The Crown Prosecution Service (CPS) appealed for the sentence to be increased and, giving his judgement, Lord Chief Justice Igor Judge said the CPS was right to mount the challenge.

However, he said Gordon had complied with every requirement of the order handed to him and it would be "unfair to impose a sentence that would interfere with his rehabilitation".

Gordon attacked Jitandra Patel in his Melton shop in September, stealing £670 cash.

He wounded the shopkeeper after the 52-year-old tried to stop him taking money from the till.

The 33-year-old, of Longcliffe Hill, Old Dalby, Melton, admitted robbery, having a bladed article and possessing a Class A drug at Leicester Crown Court, in March. He had spent 185 days in custody following his arrest. Gordon was sentenced to an 18-month community order with supervision by Judge Michael Pert QC, and ordered to attend a 12-month drug rehabilitation course and a substance abuse programme.

The CPS had prepared a report for the Attorney General containing reasons why the sentence was, in its opinion, unduly lenient.

Refusing to increase the sentence, Lord Judge said: "The appropriate sentence should have been one of immediate custody.

"The message must be clear – shopkeepers performing valuable services to their communities must be protected."

However, he said Gordon should be given the chance to rid himself of drugs and the community order would remain in place.

"This is a man who looks as though he is starting to become rehabilitated and who is obeying the conditions attached to the community sentence.

"All the evidence suggests there are indications the process of rehabilitation is well under way, although not complete."

The court was told Gordon joined the Army at the age of 18, but left shortly after three of his colleagues were killed by a car bomb in Northern Ireland.

He was left suffering from post-traumatic stress disorder and developed a drugs problem.

After the hearing, district crown prosecutor Lawrence English said: "While we appreciated the defendant's mitigating circumstances in that he had post-traumatic stress disorder, we considered the seriousness of the case and the impact of the attack on the victim to outweigh that. We believed the sentence to be insufficient for the severity of the crime.

"Although today's hearing has not resulted in a custodial sentence, we are pleased our decision to refer the case to the court was deemed to be the right one and that we have taken forward every legal avenue open to us to appeal the sentence and safeguard the public."

Mr Patel said while he welcomed the news Gordon was "taking steps to clean up his life", he could never forgive him for what he had done.

He said: "It has changed my life and made me wary of everyone who comes into the shop.

"It's not a very friendly way to live, all because of what one person did. I hope he uses the opportunity to clean himself up."