Jeffrey Gafoor was free for 15 years after "systematic failure"

Alex Carlile QC also believes control of the police should be taken away from Westminster and given to the Welsh Assembly Government.

Lord Carlile spoke out amid calls for a public inquiry into the original investigation into the brutal killing in Cardiff in 1988.

Security guard Jeffrey Gafoor, 38, of Llanharan, south Wales, was jailed for life on Friday after admitting the murder.

But there is anger that five innocent men were tried for the crime, and that three of them were jailed. They were subsequently freed by the court of appeal.

Many people... would favour the establishment of a single police force for Wales Lord Carlile

Lord Carlile, who is also a former leader of the Welsh Liberal Democrats, said public confidence in the police had been "knocked".

'Systematic failure'

"This opens a much wider question in my view about the organisation of the police in Wales," he told BBC Radio Wales.

The Lynette White investigation led to wrongful convictions

He said control of the fire service had recently been handed to the assembly government, and there was no reason the same should not happen with the police.

"I believe that expertise which is available in all Welsh police forces including, of course South Wales Police, is not focussed properly," he said.

Lord Carlile said on Good Morning Wales there had been a "systematic failure" in the way South Wales Police had investigated murder cases.

"There are many people in Wales who despite the inevitable political arguments that would ensue would favour the establishment of a single police force for Wales covering Wales' two and three quarter million population," he said.

Cardiff North MP Julie Morgan said she was also worried by other cases in south Wales.

'Huge relief'

These included the Cardiff Newsagent Three, who were wrongfully jailed for the murder of newsagent Phillip Saunders 15 years ago, and cleared more than 10 years later.

Lord Carlile says Welsh police expertise is not focussed properly

South Wales Police have reopened the investigation into the murders of Harry and Megan Tooze, an elderly couple shot dead at their farm in Llanharry in 1993. Their son-in-law, Jonathan Jones, was jailed and cleared on appeal.

"Thankfully now in the Lynette case we've actually got a judgement which must be a huge relief to the Lynette White family, but there's still questions about how that investigation took place," said Mrs Morgan.

She has written to the chief constable of South Wales Police on behalf of the Newsagent Three.

"When people have spent years in prison for something they haven't done and nothing is done to end the process, nobody says I'm sorry we made a mistake, we did the wrong thing, and I think that should be done," she said.

John Charles Rees QC, who was a defence lawyer in the original Lynette White trial and also represented her killer Gafoor, has called for a public inquiry and a police apology to the five men originally arrested.

The Bar Council's Andrew Taylor also said there should be a public inquiry.

'Utter fantasy'

Mr Taylor said two prostitutes had told the first trial they had seen the five men taking part in the murder and claimed they were forced to take part themselves.

Mr Taylor said: "People must be investigated for perjury and for perverting the course of public justice.

"Because it's inconceivable, I suggest, that people would come forward and give those accounts when of course we know they are complete and utter fantasy unless perhaps somebody suggested that that's evidence the police and others wanted to hear."

Lord Carlile said it was very unusual for a QC who had appeared in a case to call for a public inquiry.

But he doubted that a public inquiry would be feasible to bring people to account, because that could prejudice future criminal proceedings.

However, he would support an independent inquiry, probably chaired by a judge or senior lawyer.