THE impartiality of civil servants in Scotland in the run-up to the independence referendum is to be examined by MPs.

Although the focus will be north of the Border, members of the Commons Public Administration Committee have called for views on the roles of Whitehall-based Sir Jeremy Heywood, the UK Cabinet Secretary, and Sir Bob Kerslake, the head of the UK Civil Service.

The latest probe into matters relating to independence could spark controversy: its title specifically says "civil service impartiality in Scotland"; and the inquiry will seek views on the role of civil servants in compiling the Scottish Government's White Paper.

While civil servants north of the Border were involved in compiling the Scotland's Future document, those south of the Border engaged in drawing up the analysis papers addressing various policy areas in relation to the possibility of Scottish independence and highlighting the benefits of the Union.

In 2011, Sir Peter Housden, the most senior civil servant in Scotland, was called on to resign after claims he had become too close to the SNP Government, and had been advising Alex Salmond and his ministers on tactics and policy in relation to independence.

But Lord O'Donnell, the civil service chief at the time, cleared Sir Peter, stressing it was the job of civil servants to support the elected government of the day.

Last week, the impartiality of another top civil servant was called into question when John Swinney, the Finance Secretary, said Sir Nicholas MacPherson, Permanent Secretary at the Treasury, had "crossed the line" by giving advice to George Osborne, which the Chancellor used to rule out the First Minister's preferred option of a currency union between an independent Scotland and the rest of the UK. The Treasury defended Sir Nicholas, insisting his advice had been completely impartial.

Last year, in evidence to the committee, Sir Peter set out the "two-fold" responsibilities of civil servants in Scotland: to "deliver the policies of the elected Government of Scotland, which includes delivering the current Scottish Government's purpose of creating a more successful country by increasing sustainable economic growth with an opportunity for all of Scotland to flourish"; and to "act with integrity, impartiality, objectivity and honesty".

The inquiry will look at the dual obligations of civil servants in the Scottish Government to their ministers and to the UK Civil Service as a whole and explore what "impartiality and objectivity" mean in practice for civil servants working on the referendum.

The inquiry is expected to begin in April.