The Prime Minister is preparing to face down threats to his leadership by telling his enemies that they should not be playing politics at a time of economic troubles.

Gordon Brown returns to the fray tomorrow after a three-week break with a plan designed to show that he is the politician best placed to lead Britain through the downturn, and that he is ready to take on his critics.

But Mr Brown has been planning his relaunch without knowing whether the plotters seeking to remove him from office will strike again over the next few weeks.

His allies are waiting to see if his opponents, emboldened by David Miliband's move to display his leadership credentials, begin a fresh campaign in the run-up to the Labour conference to destabilise him in the hope that it will force him out.

Mr Brown has been involved in Whitehall discussions over the summer to help people worst affected by the surge in fuel and food prices and the slowdown in the housing market.

Some of the announcements will come before Alistair Darling's Pre-Budget Report in the autumn. But ministers and senior figures close to Mr Brown are also braced for attack from his senior backbench critics, such as Stephen Byers and Charles Clarke, and are uncertain whether Mr Miliband's decision to present himself as a runner will prompt any Cabinet move against the Prime Minister.

Mr Brown's supporters intend to fight any manoeuvring by:

— Telling the critics that they are playing politics at a time when the country is expecting them to be concentrating on helping it through difficult economic times.

— Warning that they are damaging the unity of the Labour Party and playing into Tory hands because disunited parties are certain to lose elections.

— Pointing out that the dissidents are “ultras” who are not representative of opinion in the party and country.

Mr Brown will also hold the threat of a reshuffle over the Cabinet as he attempts to maintain discipline, although his preference is to delay it until October, The Times understands.

The prospect of a reshuffle is one of the few weapons at the disposal of a beleaguered Prime Minister, enabling him to take swift revenge for, or even pre-empt, disloyalty.

Ministers were taken by surprise by Mr Miliband's open emergence as a leadership contender in the days after the Glasgow East by-election defeat and admitted that they do not know how events will unfold.

Mr Brown believes that a reshuffle next month might look inappropriate at a time when he is focusing on people's domestic concerns. But he will not rule it out until he sees how his critics are behaving. A series of initiatives are being planned within government departments after Mr Brown told them that the Government must be seen to be responding to the worries of ordinary people.

Although he has thought about a reshuffle during his Downing Street absence, it has not apparently been at the top of his agenda. He thinks that the challenges facing the country are so important that ministers' energies should be concentrated on them.

Another reason for delaying the reshuffle is that Mr Brown would prefer his senior ministers to concentrate on the relaunch rather than worrying about their futures. There has been speculation that Mr Brown might give Mr Darling and Mr Miliband a job swap to bind in Mr Miliband. But Mr Darling is unlikely to be moved.

One minister who has not helped his job prospects is Ivan Lewis, the Health Minister, who suggested in an article yesterday that the Government should consider a tax on the rich to ease the burdens of lower and middle-income families, an idea that has no chance of being adopted. Downing Street and the Treasury did not comment on his proposal, but a government source said: “Ivan should concentrate on his day job; otherwise he might not have a job at all.”

With Labour's annual conference starting earlier than usual this year on September 20, senior ministers would have little time to prepare for speeches in their new roles if the shake-up took place in early September.

Even so, the timing of the revamp will depend on how Labour responds to Mr Brown's fightback. He will return to the front line next week as he visits Beijing for the last few days of the Olympic Games and the handover to London.

Mr Miliband broke into his holiday last week to deal with the response to the Georgia crisis and spoke to Mr Brown on the telephone. He later praised Mr Brown's “vigour and determination”.

Other ministers who have spoken to Mr Brown say that he is in a determined mood. One told The Times: “If anyone thinks Gordon is going to roll over and let his critics push him out, they could not be more wrong.”

Another said: “He knows, we all know, that his speech to the conference is the most important of his life.”

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