Leaders call for independent probe in tartan tax row
First Minister Alex Salmond has been urged to open up the Scottish government's handling of tax-varying powers to independent scrutiny.
Labour leader Iain Gray and Lib Dem leader Tavish Scott have written to ask him to refer the matter to a panel of former Holyrood presiding officers.
It emerged recently that ministers would be unable to increase or reduce tax for the next three years.
The opposition leaders want to know if the ministerial code was broken.
Last week, Mr Salmond and Finance Secretary John Swinney apologised to the Scottish Parliament for not keeping MSPs informed about the loss of the tartan tax powers.
The deal, which allowed Scotland to raise or lower income tax by 3p in the pound, was allowed to lapse in 2007 and cannot be used until 2013-14.
The Scottish Parliament last week passed a motion accusing SNP ministers of "an abuse of power" by failing to sustain Holyrood's tax powers and misleading parliament over the issue.
In a rare joint letter, Mr Gray and Mr Scott said: "We are concerned that Scottish ministers knew that the tax-varying powers were not capable of implementation yet persisted to present to MSPs and others the impression that the powers were ready to use."
The letter continued: "While ministers have apologised for the length of time they took to bring the matter of the Scottish Variable Rate to parliament, our complaint is about the conduct of ministers and the government in the misleading information they provided to parliament."
The opposition leaders said they considered it "entirely appropriate" that an investigation be held into whether ministers breached the ministerial code of conduct.
"We ask that our complaint be referred to the independent advisers on the ministerial code, the former presiding officers George Reid and Lord Steel," their letter added.