Prime Minister Gordon Brown received a welcome double boost to his ailing fortunes Saturday when Harry Potter-author Joanne K. Rowling revealed a massive donation to the ruling Labour Party as key ministers rallied around their leader.

As Labour's annual party conference got under way in Manchester, northern Britain, the man tipped to be the most likely contender for Brown's job, Foreign Secretary David Miliband, made a rousing call for unity in the face of economic adversity.

"It is time for the party to come together. I've made it clear I don't think it's the time for a leadership election," Miliband said.

The 43-year-old "Labour star," who is considered to be the frontrunner in a possible challenge to Brown, said the conference was "a five-day opportunity for the party to put a strong, determined, clear, unified face before the public."

The words will have been music to Brown's ears after months of relentless attacks on his allegedly weak leadership and an attempt by a handful of junior government ministers last week to seek a leadership contest in Manchester.

But with cabinet ministers staying loyal to Brown - at least in public - the attempt at a "coup" faltered.

However, of much greater importance to the ailing leader is the support from Rowling, a personal friend of Brown and his wife, Sarah, who has now openly revealed her support for the Labour Party.

Rowling's support is more than financial - it carries symbolic significance as a rare public demonstration in favour of Brown - which has been so noticeably absent over the summer months.

Rowling revealed that she had donated one million pounds (1.25 million euros) to the Labour Party because she approved of the government's policy on combatting child poverty.

Private donations to Labour have all but dried up after a series of scandals, and the party's financial dependence on the trade unions is now as great as in the 1970s, analysts believe.

Membership of the Labour Party has halved to below 200,000 over the past decade, and its debts are estimated to have risen to around 18 million pounds.

Private donors, among them graffiti artist Banksy, have donated in total 3.8 million pounds to the party between April and June this year, it was revealed Saturday.

Rowling, who is said to have amassed a fortune of 560 million pounds, was a single mother on social welfare when she started writing Harry Potter in a cafe in Edinburgh, the Scottish capital where she now lives, and where Brown also has a home.

However, there were signs Saturday that the public and prominent support for Brown on the opening day of the conference did not mean the end of all trouble for the prime minister.

An opinion poll published Saturday in the Daily Telegraph showed Labour trailing behind the Conservatives by 20 points.

Brown also received poor personal ratings, with just 16 per cent of those asked saying they believed he was providing strong leadership.

During a keynote speech to delegates next Tuesday, Brown is expected to say that he is the right man to guide Britain through difficult economic times, and that Labour should put aside its squabbles to tackle the challenge together.