Cardinal Keith O’Brien, the former leader of the Scottish Catholic Church, could end up facing a criminal inquiry following allegations of sexual misconduct involving several priests over a period of thirty years.

Police received a formal complaint yesterday against the cardinal, who on Sunday night admitted that his “sexual conduct” had been “below the standards expected” of him.

Lawyer Nick Freeman, well-known for representing a string of celebrities, has now called on police to investigate.

The Catholic Church has launched its own internal investigation but Mr Freeman, dubbed ‘Mr Loophole’ for his success in helping clients avoid driving bans, said he wanted to ensure that if “any criminal activities had taken place they would be investigated fully”.

He said: “After listening to the admissions of Cardinal O’Brien, I felt compelled to make a formal complaint in order to trigger a full criminal investigation.

“I was shocked to hear there is to be an internal investigation only. This will be heard behind closed doors and the full findings would not be published.

“This isn’t justice. Justice needs to be seen to be done and the Catholic Church has a moral and legal obligation to co-operate fully with any criminal investigation.”

Last Friday, it emerged that a fifth claim of “inappropriate behaviour” towards a male priest had been made against Cardinal Keith O’Brien.

Meanwhile, Britain’s leading gay rights campaigners say the former leader of the Scottish Catholic Church should also apologise to gay people for his “vicious and cruel language” about them.

On Tuesday, Human rights campaigner Peter Tatchell said: “Cardinal O’Brien’s admission of sexual contact with men torpedoes the credibility of the church’s bigoted stance against homosexuality. It also undermines the campaign against same-sex marriage.

“It will be very difficult to take the opponents of marriage equality seriously now that this senior spokesperson has admitted that he did what he preached against.”