COLIN Boyd, the lord advocate, was yesterday made a working peer in the House of Lords, fuelling the debate about the independence of his role as head of the prosecution service in Scotland.

Questions were also asked of his ability to carry out this new function while still retaining his other role as legal adviser within the Scottish Cabinet.

There was confusion over the status of Mr Boyd, with the Crown Office stating that he would become a Labour working peer, while Downing Street said that he would sit as a crossbencher.

Mr Boyd said: "It is a great honour, both personally and professionally, to be appointed to serve in the House of Lords. I look forward to playing an effective role in policy-making for the UK, especially in relation to Scottish affairs.

"In particular, I will be in a position to make a significant contribution to debate on reserved issues which affect Scotland. The ability to represent in the House views which are relevant to my duties as a Scottish law officer is welcome, and I will take all opportunities to make useful contribution to debate in this regard.

"I remain firmly committed to the full-time role of lord advocate, leading the Crown Office and procurator-fiscal service, and seeing through the programme of reform I initiated four years ago. I see the appointment to the House of Lords as a natural extension of my duties as lord advocate."

Nicola Sturgeon, SNP leader at Holyrood, said: "The role of lord advocate is already too political by being in Cabinet, I fear this may make it worse. The time has come for the lord advocate to become genuinely independent of politics and not a member of the Cabinet."

David Mundell, the Tories' shadow Scottish secretary, said: "This shows the complete contempt Labour has for the House of Lords and the institutions of democracy. Either Colin Boyd is a member of the government or he is a crossbencher - he can't be both."

Mr Boyd was one of seven Labour nominations, while seven Tories were appointed along with five Liberal Democrats, one Ulster Unionist and three Democratic Unionists. Labour now has 221 peers, with the Tories and Liberal Democrats combined with 295.

Margaret Ford, chairwoman of English Partnership and former chairwoman of Lothian Health Board, and executive director of Scottish Homes, was another Labour nomination.

The new list revealed that Tony Blair, the prime minister, abandoned attempts to appoint more Labour than Tory peers in the wake of the controversy over loans for peerages.

Mr Blair had nominated four businessmen who bankrolled Labour during the general election campaign, but they withdrew their names amid a media outcry over their financial arrangements with the party.

It is understood the four, as well as one Tory, were or would have been blocked by the Lords Appointments Commission, which makes recommendations to Mr Blair.

Sir Bill Morris, former leader of the T&G union, and Maggie Jones, Unison's director of policy and public affairs, who failed to become an MP at the general election, were both elevated to the Upper House.

David Trimble, former Ulster Unionists leader, will become a peer and, in a departure from tradition, there will be three DUP nominees, one of whom is Eileen Paisley, the vicepresident of the party and wife of Ian Paisley, the DUP leader.