UK's Brown faces leadership challenge after Labour's thumping by-election defeat

"What I want to show over the coming months, and whenever the general election is, is that that trust is right and that we will not let those people down. I want to build over the coming months, over the coming years, the biggest coalition for change in our country so that we really can change the country, we really can remove this government and give Britain a better chance," the opposition leader said.

"I want to go on building this broad coalition for change so we can bring our country better government," he said, calling the Labour government "backward-looking and divisive."

Meanwhile, calls for Brown to step down is getting louder even as he faces increasing leadership challenge.

Many Labour MPs feel last week's Crewe and Nantwich by-election defeat reflects that the party's popularity has slumped to record lows and it is time to think about "fresh leadership" if the Labour Party is to harbour any hope of winning the general election.

The by-election was called after the death of veteran Labour MP Gwyneth Dunwoody and her daughter Tamsin was soundly beaten by Conservative candidate Edward Timpson.

Those tipped to give Brown a run for his money are Foreign Secretary David Miliband, Justice Secretary Jack Straw and Transport Secretary James Purnell. Though none of them are going to publicly challenge Brown's leadership, their supporters will be making it clear to everyone that there is an alternative to Brown.