The Commission on Scottish Devolution will not �rubber stamp� a pre-determined agenda, according to Sir Kenneth Calman, the man leading the investigation into whether more powers should be devolved to the Holyrood parliament.

The Commission on Scottish Devolution will not "rubber stamp" a pre-determined agenda, according to Sir Kenneth Calman, the man leading the investigation into whether more powers should be devolved to the Holyrood parliament.

Under close questioning from members of the Commons Scottish Affairs Committee yesterday, Sir Kenneth assured MPs that his investigation would be politically independent.

"We were set up with a clear remit, we were not under any pressure from any source to come to a pre-determined outcome," Sir Kenneth told sceptical MPs who felt his presumption was to recommend more powers for the Scottish Parliament.

"We are open, we have no presumptions, let us know what you and your constituents think and we will consider it," Sir Kenneth said. "If there is evidence that it would be useful for power to come back to Westminster we will consider that - but it has been quite difficult to find it."

Ian Davidson MP, Glasgow South West, led the attack and questioned the credibility the commission's members. "It is nonsense to suggest that this is an objective analysis. There are a whole number of people on the commission whose opinions are known and you can almost work out just now what the score is going to be on a number of issues," said Mr Davidson. "This is essentially a rubber stamp."

David Mundell MP, Shadow Scottish Secretary, wanted to know how representative responses to the consultation would be. "People who tend to e-mail the Scottish national newspapers in the middle of the night aren't necessarily representative of the people of Scotland," said Mr Mundell.

Sir Kenneth said all opinions represented a legitimate position but his investigation would focus on specific issues that people could respond to. However, he had difficulty persuading MPs that only those motivated by independence would engage with the commission.

Mr Davidson pressed the point home: "How do we know the people you are consulting are genuinely representative of anyone but themselves."

Charles Walker, the Conservative MP for Broxbourne, expressed concern that his English constituents, whose opinions on Scottish independence were equally valid, were not represented on the commission, so he invited Sir Kenneth to take evidence in England.

"I am surprised that this is so Scottish-centric," said Mr Walker. "I'd be happy for you to come to Broxbourne where I could organise a reception committee," he added to laughter. Sir Kenneth agreed that it was important to hear views from outside Scotland. "Many of the task groups will have people from outside Scotland," he said.

Sir Kenneth sidestepped questions on an independence referendum posed by Angus MacNeil of the SNP, who asked if Scottish Labour leader Wendy Alexander's call for an immediate vote on the issue had undermined his work? "I think what it did was make the commission more important rather than less important," said Sir Kenneth who repeated that considering independence or a referendum was not the remit of the committee.

Sir Kenneth revealed he had written to the First Minister Alex Salmond to gain an insight on the first year of his administration and had received a positive response. The SNP government is running its own parallel "Scottish Conversation" consultation on the future powers of the Scottish Parliament.

Sir Kenneth announced an expert independent group will advise on finance, including the Barnett formula that determines the level of central funding to the Scottish Parliament.

Several English Labour MPs have signed an early day motion at Westminster calling for a review of the formula and the Treasury is expected to prepare a paper clarifying the funding arrangement in the near future. An interim report from the Calman Commission is also due at the end of this year with a final report drafted, according to Sir Kenneth, "sometime in 2009".