A SENIOR adviser to Alex Salmond has left his post at a crucial point in the referendum campaign.

The First Minister has lost his head of policy, Alex Bell, following the departures of senior figures at the Yes Scotland campaign in recent weeks.

Mr Bell was a key member of the team of special advisers at the Scottish Government's headquarters, St Andrew's House in Edinburgh.

Government sources insist he was not forced out. He was not responding to calls last night.

The move follows the departure of two senior figures at the pro-independence Yes Scotland campaign. Jacqueline Caldwell left as director of operations without fanfare earlier this year, while Susan Stewart left as director of communications last week amid claims that the campaign was beginning to run into financial difficulties.

Although it does not apply to the Scottish Government, any appointment of an additional adviser would have been attacked by Mr Salmond's opponents.

The shift sees the Government boost its media team with the appointment of long-standing political journalist Campbell Gunn in place of Mr Bell, replacing a back-room strategist with a front-office publicist.

It is being suggested that having completed the policy work for the White Paper on independence in September, this is now moving into the delivery phase using Mr Gunn to sell the package to former colleagues in the press corps.

The former long-serving political editor of the Sunday Post is a popular figure among his former colleagues but he will know this will be a tough sell to a largely hostile audience.

A spokesman for the First Minister said: "Campbell brings a wealth of experience to the special adviser team, which will be a huge asset. Alex's contribution has been significant, not least in helping secure the Edinburgh Agreement, and we wish him well in his future endeavours."

Mr Gunn will be braced for tough questioning, particularly when the White Paper is published in September.

The Scottish Government stresses that the cost of its team of Special Advisers has been cut in real terms by around £54,000 between 2006/07 and the end of last year – and compares to a pay bill of more than £6 million for the UK Government's special advisers at Westminster, where costs rose by almost 40% in a single year as a result of the coalition.