BBC Scotland was forced to defend its political coverage last night after a senior reporter revealed she was in a relationship with a Liberal Democrat minister, but was to carry on in her current role.

Kirsten Campbell, BBC Scotland's political correspondent, and Tavish Scott, deputy finance minister, yesterday announced they had been romantically involved for around six weeks.

The couple are understood to have made the declaration amid mounting speculation.

Mr Scott, 37, MSP for Shetland, is separated but not divorced from his wife of 14 years, with whom he has three children.

He said: ''Given media interest in my separation last year, I have decided to avoid any speculation by confirming that I am in a relationship with Kirsten Campbell and have been since last month.''

He refused to give further details or say if an engagement was being planned.

Ms Campbell, 35, added: ''It's early days. I consider myself lucky to have found such a wonderful man.''

She said she told her employers of the relationship around two weeks ago to ensure there was ''no question of any impact on my integrity or credibility, or the BBC's integrity or credibility''.

She added: ''If this relationship becomes serious then I will have to move out of political coverage.''

The announcement drew immediate comparisons with Elizabeth Quigley, the BBC political correspondent who switched to general news reporting after announcing she was involved with John Swinney, the SNP leader.

Their relationship became public in August 2001, and they married in July 2003.

However, the BBC last night said that Ms Campbell would continue to cover the Scottish Executive, in which Mr Scott has a number of important duties and uniquely covers two portfolios.

As deputy finance minister, he has responsibilities for the Scottish budget, public services, local government, civil service reform and external relations.

As deputy minister for parliamentary business, he is involved in organising Holyrood's legislative programme.

The BBC said Ms Campbell would not cover stories involving Mr Scott personally.

A spokesman said the corporation ''absolutely'' stood by the integrity of its output.

He said: ''We all know Kirsten Campbell is highly regarded and known for her impartiality and lack of bias, as is the case for all our political correspondents.''

There was little anger or surprise at the development at Holyrood last night, where Ms Campbell is respected by MSPs and journalists.

Mr Scott now joins the growing list of senior MSPs who have or have had partners in the media, including Susan Deacon, the ex-health minister, Rhona Brankin, ex-fisheries minister, and Tom McCabe, deputy health minister.

The Scottish Socialist party said it was happy for Ms Campbell, but would monitor her broadcasts with interest.

A spokesman said: ''We are not interested in who has a relationship with who. What we are concerned about is the integrity of the political output of the broadcasters.

''We will continue to monitor them for any signs of bias.''

The SNP and Tories both declined to comment on the matter.