Gordon Brown made a secret offer to bring Liberal Democrats into his first Government as ministers in the Lords, The Times can reveal.

Paddy Ashdown, the former Lib Dem leader and an expert on international affairs, was top of the list of peers targeted by Mr Brown.

The plan applied only to certain Lib Dem peers and they would have been offered posts up to the level of Minister of State and not seats in the Cabinet. Lib Dem MPs would not have been included.

Lord Carlile of Berriew, QC, a prominent barrister who already acts as the Government’s independent assessor of counter-terrorism legislation, is another likely candidate, as is Lord Lester of Herne Hill, a human rights lawyer who has led the way on several pieces of reforming legislation.

The offer was made by Mr Brown at a meeting with Sir Menzies Campbell on Monday evening, in the Chancellor’s office and arranged at his request.

Sources close to Mr Brown said the Lib Dem leader undertook to go away and discuss the plan with his advisers, including his close friend Lord Kirkwood of Kirkhope and chief of staff Ed Davey.

Labour MPs suspect it was leaked deliberately by other Lib Dems in attempt to kill the move. Despite the leaking of his proposal, however, allies of Mr Brown insisted that he remained committed to a broader approach to government.

Mr Brown and Sir Menzies, who are long-time friends and have neighbouring constituencies in Fife, also had a general discussion about the Prime Minister-in-waiting’s plans for constitutional reform and his wish to involve a wider range of people in Government decisions.

Sir Menzies appeared to close the door on the idea of Lib Dem ministers today as he issued a statement ruling out any member of his party joining the Government after Mr Brown becomes Prime Minister after the resignation of Tony Blair on Wednesday next week.

“There is no prospect of any Liberal Democrat joining the Government,” the Lib Dem leader said.

Mr Brown’s surprise offer explains his remark on accepting the nomination as the sole candidate to be Labour’s next leader last month that he wanted to lead “a Government of all the talents”.

One of his allies said: “He asked Ming whether he would have any objection to him approaching members of his party in the Lords with a view to them serving on the front bench.”

He was specific that the offer did not extend to seats in the Cabinet nor to any of the 63 Lib Dem MPs in the Commons.

A source close to Mr Brown confirmed that they discussed Lord Ashdown of Norton-sub-Hamdon, who returned to Britain last year after four years serving as the European Union’s high representative for Bosnia.

Lord Ashdown is regarded as an expert on international affairs and conflict resolution, if something of a hawk, and was one of the few senior Lib Dems to have backed the Iraq war.

Lord Ashdown himself had lengthy negotiations with Mr Blair before the 1997 election with a view to taking his party into a full Lab-Lib coalition, including up to four seats in the Cabinet, but the plan was eclipsed by the scale of Labour’s majority in the Commons.

At the time, and during subsequent looser discussions between the parties during Mr Blair’s first term, Mr Brown was seen as a sceptical to such cross party collaboration.

But the Lab-Lib co-operation was founded on an agreement between the parties on a joint programme on constitutional reform, spanning a human rights law, devolution for Scotland, Wales and London and freedom of information laws, although it foundered over Lords reform.

It is this cross-party co-operation on constitutional reform that Mr Brown may be seeking to revive as he prepares to embark on a new programme to include codifying Britain’s unwritten constitution, giving Parliament the final say on committing British troops to war and another attempt at Lords reform.

Two months ago Sir Menzies rebuffed another offer of cross-party collaboration, this time a proposal from David Cameron that the Conservatives and Lib Dems jointly back Greg Dyke, the former BBC Director General, as an independent candidate for London mayor.

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