Ken Macintosh, the Labour MSP for Eastwood, has blamed a statistical glitch after emerging as one of the Scottish Parliament's biggest expenses claimants.

The parliament has long operated a very tight regime on expenses and it has been further constricted over the years to the point at which only the remoteness of constituencies from Edinburgh has tended to account for the amount spent by MSPs.

So the fact a constituency just outside Glasgow turned up sandwiched between the Orkney and Shetland MSPs raised eyebrows at Holyrood when expenses for 2012-13 were published online.

The Liberal Democrats representing the Northern Isles were at numbers one and three on the list, with Orkney's Liam McArthur claiming £46,931 and Shetland's Tavish Scott on £40,967. But sandwiched in between with a claim of £42,474, was Mr Macintosh.

His spokesman insisted: "Mr Macintosh's expenses have not increased at all. This is simply the way the Scottish Parliament has accounted for part of his staffing last year. Without it Mr Macintosh would be 36th out of 129 MSPs."

But the Scottish Parliament figures were defended by a spokeswoman, who said the totals on the website were accurate and it was up to MSPs how they hired staff.

If they are taken on directly as employees they go into the overall budget of the Parliament and are not identified for data protection reasons.

But if an MSP chooses to hire staff on a contract basis and invoices the Parliament for this, then this expense appears within the MSP's own figures.

Ten MSPs spent £44,211 on contract staff last year but most involved small sums. Two accounted for in excess of £16,000 each - Mr Macintosh, and the SNP's South of Scotland list MSP Chic Brodie.

Mr Macintosh's invoices were for payments to Labour's Members' Support Unit, while those from Mr Brodie were to a firm called Caledonii Resources.

Margo MacDonald, the Lothian independent, was again Holyrood's most prudent member, with claims of only £2627. She was followed by other Lothian list MSPs Kezia Dugdale and Sarah Boyack of Labour, and Gavin Brown and the late David McLetchie, from the Conservatives.

The Parliament's total expenditure last year on MSPs' salaries, expenses, and staff costs was £12.2 million, down by more than £500,000 from the previous year, largely because of winding up costs when seats changed hands then.

The total of £12,261,819 for 2012-13 is £557,016 lower than the £12,818,835 claimed the year before. This represents a 4.35% fall before inflation is taken into account.

A Scottish Parliament spokesman said: "The decrease in expenses of more than £500,000 is a reflection of one-off election costs in the previous year, but also that 2012-13 represented year two of a two-year pay and expenses freeze for MSPs."

A total of 48 MSPs claimed winding-up expenses in 2011 because they stood down before the elections or lost their seat.