Plans to give an extra member of staff to constituency MSPs but deny this to their regional list counterparts must be overturned, according to the most experienced politician on the review panel.

Plans to give an extra member of staff to constituency MSPs but deny this to their regional list counterparts are based on flawed research and must be overturned, according to the most experienced politician on the review panel.

The idea of widening the disparity in resources between constituency and list MSPs has caused deep divisions at Holyrood both between and within parties.

Now further concern has been raised about the evidence behind the proposals. Holyrood research staff spent a day last summer shadowing two long-serving constituency MSPs but the regional list member they selected for comparison had been elected only in May, giving him no time to build up a case load.

Following the publication last week of the report by the Allowances Review Panel, chaired by Sir Alan Langlands, Lord Selkirk of Douglas, a former Conservative MSP and Westminster minister, insisted that his dissent was recorded.

"One of the reasons I was so determined to dissent was that I believed the evidence before us was extremely limited," said Lord Selkirk. "We only had a very limited sample to work on and my view was that this was just too small to make a judgment. I could see there was some evidence that more constituents tend to go to their constituency MSP than to a list member with a problem, but the allowances at the outset were not identical between the two categories of MSP and I objected in principle to them widening the gap further."

Present staffing costs are included with accommodation in a support allowance, with regional MSPs receiving less to reflect the fact they are often expected to share offices.

Within that, the notional staffing allowance is around £45,000, to cover one-and-a-half posts.

Now it is proposed to give constituency MSPs £62,000 to cover two-and-a-half posts, leaving list members at the current level. Lord Selkirk said that had the ratio been set at two-and-a-half and two, he could have accepted that.

But the other four members of the group, including the only other politician on the panel, Tom McCabe, the Labour MSP for Hamilton South, backed the proposal.

The SNP's South of Scotland list member, Christine Grahame, was furious at the examples taken for the shadowing exercise.

The two constituency members, the SNP's Andrew Welsh in Angus and Labour's Sarah Boyack in Central Edinburgh, were both in their third term at Holyrood but the regional list member selected was West of Scotland Tory Jackson Carlaw, who had barely had time to get his office up and running last summer after being elected in May.

"How could they possibly compare two constituency MSPs who have been in office for more than eight years with a regional list MP who only came into office last May and cannot possibly have had time to build up a full case load? It's ridiculous," said Ms Grahame.

"They are basing their recommendation on false evidence.

"There will be some constituency members who have a bigger caseload than regional members but it will also be a fact that some regional MSPs will have a bigger caseload than some constituency MSPs. Is the logic here that MSPs for the islands should get less money because they have fewer constituents?"

A spokesman for the Scottish Parliament said: "Evidence was received from a total of 104 public submissions, including 48 from members and 18 from members' support staff.

"Evidence was also received from research reports and first-hand experience - three members of the panel spent time in members' local offices. Every MSP will have the opportunity to debate and vote upon the detail of any new scheme."