Tony Blair made detailed preparations for sacking Gordon Brown from the Treasury in the run-up to the last general election, it was reported today.

A leaked document provides the first hard evidence that the Prime Minister intended to dismantle the Chancellor's power base, according to the Independent on Sunday.

Secret Cabinet Office plans spell out how Mr Brown would be moved to a lesser portfolio, while his former department was broken up and had many of its responsibilities removed.

The revelations could undermine the "stable and orderly transition" to Mr Brown which will culminate when he becomes Labour leader today, and then enters Number 10 on Wednesday.

At his final Cabinet this week Mr Blair pledged "unswerving loyalty" to his successor, but there has long been speculation at Westminster that he considered politically assassinating him two years ago.

The confidential document from March 2005, obtained by the newspaper, was prepared by a handful of civil servants including trusted advisers in the Prime Minister's Strategy Unit, along with former BBC director general Lord Birt.

It features step-by-step actions to be followed when carrying out the radical reorganisation, as well as draft speaking notes for the Prime Minister a briefing for the "new Chancellor".

There is also a list of the qualities Mr Brown's replacement in Number 11 should possess - such as a "lack of personal investment in previous policies". It adds that "teamwork" is a key asset - something which Blairites often complain the premier-in-waiting lacks.

The proposals suggest that Mr Brown was to be kept in the dark about the changes afoot, while his own civil servants would be asked to work on the plans without telling him.

On the new Chancellor's first day in office Mr Blair should inform him of his plans for splitting the Treasury and handing many of its roles - including responsibility for tax credits - to other ministries, according to the document.

The department's ability to spend money would be removed because it had "caused a conflict of interest".

The disclosure underlines the stormy relationship between Labour's two most powerful figures over the past decade.

They are widely regarded to have been at drawn daggers in the period before the 2005 ballot, when Mr Blair sidelined Mr Brown by placing his ally Alan Milburn in charge of the campaign.

However, slumping poll ratings soon forced the PM to reinstate Mr Brown as campaign boss.

His subsequent success in delivering an historic third term for Labour and Mr Blair is believed to have led to the proposals being ditched.

Mr Blair has now endorsed the Chancellor as his successor, and praised his qualities as a leader and politician.

A Downing Street spokeswoman said: "We do not comment on leaked documents."