STEWART Maxwell, the SNP West Scotland MSP, was hauled into the headmistress's office for a ticking off this week.

His crime? Attempting to shout down Ken Macintosh when the Labour MSP called on Presiding Officer Tricia Marwick to address what he described as the "obsequiousness" of SNP MSPs serving on parliamentary committees. Mr Macintosh's point of order at the end of First Minister's Question was greeted with howls of indignation from the Nationalist benches. Any number of MSPs could have found themselves outside Ms Marwick's door: Mr Maxwell was singled out because he had the decency to confess.

As the spat showed, feelings are running high about claims SNP MSPs are using their control of parliament's committees to shield the Scottish Government from criticism or embarrassment. In other words, that they are failing in their parliamentary duty to hold ministers to account.

The row blew up after The Herald revealed last Saturday that the Public Audit Committee had failed to agree a report on the troubled launch of Police Scotland. Four opposition MSPs produced a minority report claiming the official version, voted through by the five SNP committee members, failed to reflect criticisms of the government aired during six months of evidence-taking. Labour's Hugh Henry, the committee convener, said other committees - which are all dominated by the SNP - had been similarly undermined. He accused SNP MSPs of belonging to a "cult of obedience and slavishness" to their party leadership.

Other complaints have emerged. SNP MSPs were accused of trying to suppress a public petition calling for independence referendums for Orkney, Shetland and the Western Isles, while the finance committee, it was claimed, withdrew an invitation to an expert witness after he produced a written submission unhelpful to Alex Salmond's case for independence. The complaints have prompted the question: is Holyrood broken and, if so, how could it be fixed?

At this point it's important to stress that SNP MSPs reject the notion that anything is amiss. A party spokeswoman dismissed the complaints as "partisan attacks" and said votes in committees produced a "democratic decision". Yet there is mounting evidence that, as the referendum draws near, the workings of parliament have become more highly politicised than ever. At First Minister's Questions SNP backbenchers now line up to ask not about issues in their constituencies but the benefits of independence. A "topical question" this week related to the actions of Labour ministers in the 1970s.

It would be ridiculous to suggest that in the past MSPs have stood completely aloof from party politicking. They have always faced a tricky task juggling dual roles as parliamentarians and party politicians. But the opposition parties believe the balance has tipped so far in recent months that proper oversight of the government is being lost.

The concerns have been growing for a while. Last year I reported on claims by Mr Henry and others that SNP backbenchers were using their committee majorities to block inquiries which might prove embarrassing for the government. The story - which, at first glance, might appear to be just so much Holyrood bubble chatter - failed to catch fire. But last December the Presiding Officer told The Herald she wanted to see committee conveners elected directly by the whole parliament rather than selected by party chiefs, in bid to reinforce their role scrutinising the work of government. The idea - which this newspaper welcomed - was roundly dismissed by Mr Henry. He claimed the SNP would simply install its favoured candidates so nothing would change.

LibDem MSP Tavish Scott, also on the audit committee, made another suggestion this week, calling for party whips to be banned from sitting on committees. The truth is, however, that while both proposals would improve a system that was already running well, neither could prevent abuse. If Holyrood is broken there is no quick fix. And that leaves MSPs like Hugh Henry with little option but to vent their frustrations in public and let people decide for themselves whether they have a case or, as the SNP insists, just a bag full of sour grapes.