A Bradford mother, jailed for the “brutal and vicious” murder of a dad-of-two, is at the centre of a campaign to change the law on the principle of guilt by association.

The case of Laura Mitchell, 27, has been taken up by campaign group JENGbA (Joint Enterprise Not Guilty by Association), and highlighted by a select committee inquiry which concluded the law on joint enterprise was confusing and in need of urgent guidelines.

Bradford South MP Gerry Sutcliffe is supporting the campaign for a change in the law.

Mitchell, then 22, her boyfriend Michael Hall and two other young men were given life sentences in October 2007 for the murder of Andrew Ayres, 50, who was attacked in the car park of the King’s Head pub in Halifax Road, Buttershaw, Bradford. They were all told they would serve at least 13 and a half years.

Judge Stephen Gullick said Mr Ayres’s death was caused by Carl Holmes, then 21, stamping on his face as he lay on the ground, leaving him unrecognisable.

The Court heard four defendants took part in a violent attack on Mr Ayres and two of his friends, following a row over a taxi. The prosecution told the jury anyone who participated in a joint enterprise with someone who causes the death of another was also guilty.

The judge said he was sentencing Mitchell, Hall, now 28, both of Bottomley Street, Buttershaw, and Henry Ballantyne, then 20, on the basis that they were secondary parties to the death. Mitchell appealed against her murder conviction, saying she had played no part in the fatal attack on Mr Ayres, had not encouraged it and had no idea that he might be killed. Her appeal was rejected.

Appeal Court judge Lord Justice Thomas said she had started the trouble that led to Mr Ayres’s death and the jury was entitled to find the murder was a joint enterprise.

Mitchell’s sister Casey Kellett, 20, and Hall’s sister, Sarah Hall, 31, said they supported the JENGbA campaign.

Miss Hall said: “This is an example of the miscarriages of justice that are occurring because the law on joint enterprise is being misused in this way, where people are being labelled murderers when they have had very little part to play in the actual murder. We think violent disorder would have sufficed as the charge in their case.

“You have to be sensitive to the fact that somebody died, but it still doesn’t mean you can sit comfortably when someone is labelled a murderer when they didn’t take part in the murder.”

Janet Cunliffe, of JENGbA, said: “JENGbA supports Laura and her family as a miscarriage of justice.”

Gerry Sutcliffe, Labour MP for Bradford South and former Justice Minister, is supporting Michael Hall’s family on the issue. He said joint enterprise was a grey area.

“Every case is different, but in this case there is a question to be asked,” he said. “You obviously feel for the victim, and it should never have happened. But I felt the links with Michael Hall were very tenuous and something we need to look at in terms of making sure justice is done. We want justice for victims, but we want it to be fair.

“We are asking the Ministry of Justice to look at the details of the case.

“It won’t happen overnight, but ultimately we are targeting a change in the law on the issue.”