Dr Richard Simpson said it was a "complex matter"

But he insisted it was "central to the bill" in terms of striking a balance between the rights of the complainer, the accused and the public.

The bill, introduced in June, would restrict the use of evidence about the sexual history and character of the alleged victim in rape and other sex crime cases.

Dr Simpson said: "If the accused has successfully argued that evidence about the complainer's past is relevant, then what about his own past?

"Can he legitimately say that while the complainer's previous behaviour is relevant his own cannot be?"

The deputy minister added that courts could already allow evidence about the accused's previous convictions when they had attacked the character of any prosecution witness.

But he pointed out that the existing provision was rarely used in sexual offence trials.

Sentencing stage

He added: "When the accused makes a successful application to introduce evidence about the complainer's character or past behaviour, the court will be required to consider disclosure or his previous sexual offence convictions."

There will be a presumption in favour of disclosure although the accused may be able to satisfy the court that it would be unfair.

The amendment would alter legislation which forbids disclosure of previous convictions before the sentencing stage.

He added: "We have not restricted the accused in the arguments he can make to overturn the presumption in favour of disclosure."

The minister insisted the amendment would not alter the accused's right to presumption of innocence and would not raise any human rights issues.

Bill Aitken pressed the deputy minister

Tory list MSP for Glasgow, Bill Aitken, expressed concern that introducing previous convictions would be "highly prejudicial to the accused" in terms of their impact on a jury.

Dr Simpson said: "The judge's direction would be very important in this respect.

"Secondly it's an inevitable consequence of this bill that the character and past behaviour of both the complainer and accused will come in and that's bound to have an influence otherwise there's little point in it coming in."

The bill would also prevent the accused from personally cross-examining the complainer, by requiring the accused to be legally represented throughout the trial.