The integrity of the Scottish legal system could be compromised if Government proposals on crime and punishment are implemented north of the border, Scotland's most senior judge has warned.

In his last address before becoming an appeal judge in the House of Lords, the Lord President and Lord Justice General of Scotland, Lord Hope of Craighead, attacked the proposed mandatory life sentence for someone convicted of a second violent or sexual offence. He said it was inappropriate for Scottish common law and could lead to “greater leniency than is justified”.

At a Law Society of Scotland conference on the white paper last week, Hope warned that prosecutors and juries, unwilling to see an offender sentenced to life imprisonment, might water down common law charges, which are not defined by statute.

“It seems to me that there is an obvious risk, in view of the way in which we practise our criminal law, that this misguided policy will achieve the reverse of what is intended and lead to greater leniency than is justified by the facts. The result will be that the judges will find themselves pronouncing more lenient sentences than they would have done if the proper verdict had been returned. All this will erode our confidence in our own system of criminal justice, with consequences which, even in the short term, could be very damaging.”

The controversial “two strikes and you're out” policy was proposed by Scottish Secretary Michael Forsyth in a white paper on crime and punishment in June. Similar measures are proposed south of the border by Home Secretary Michael Howard, and a bill is likely to be heralded in the Queen's Speech this month.

Hope criticised Forsyth for failing to consult the legal profession and defended judges' rights to speak out, saying it was “simply part of our democratic right, as citizens of this country, to say what we think, based on our knowledge and experience, about what is being proposed, in the hope that the dangers may be appreciated before it is too late”.

But Lord James Douglas-Hamilton QC, minister of state at the Scottish Office, defended the proposals. “Public opinion has too often been scandalised by lenient sentencing and premature release of offenders is deplored by the bulk of the population.”