He said the "jury was still out" on the issue as he urged the Liberal Democrats to look beyond the theory of PR to see how it works in reality.

Dr Reid said the experience of PR in the Scottish, Welsh and European elections, as well as the recommendations of a commission led by Lord Roy Jenkins, would be important as the government considered the issue.

"The jury is still out on it. It is too early. It has only been a matter of months since the (Scottish) Parliament and the Assembly in Wales was established," he told GMTV's The Sunday Programme.

'Look at the experience'

"The Government takes the whole debate very seriously. That is why we look to Roy Jenkins to put forward his recommendations.

"That is why they will form one important element of our consideration.

"So will the experience in the European elections, the Scottish Parliament and the Welsh Assembly.

"I hope the Liberals will look to experience as well, not just the theory and I'm sure they will."

'No direct link'

In Scotland, where 56 of the 129 MSPs were elected through the regional list system where they have no direct link to the constituency, Dr Reid said there had been criticism of PR.

"A system which breaks that link perhaps does not enhance democracy in a way that pure PR is intended to," he said.

Despite the criticisms, Dr Reid conceded PR had produced the Labour-Liberal Democrat coalition Scottish Executive.

"People have welcomed the fact that it threw up a system where people had to work together," he said.

'Range of issues'

"They do not necessarily agree on everything but there is a whole range of issues where two parties are coming together."

Dr Reid said new Lib Dem leader Charles Kennedy had "constructively carried forward" the policy of co-operating with Labour where the two parties agreed.

He added: "Where we agree on issues, why don't we work together?"

On the issue of concordats - statements of intent of how Whitehall departments and the devolved Scottish government will work together - Dr Reid said they would fill a valuable role

He said they were not legal documents but working arrangements.

He added: "I think you will find these arrangements will be very satisfactory from both points of view."