BIRMINGHAM, Sept 30 (Reuters) - Britain's main opposition party offered on Tuesday to support the government in dealing with the financial crisis after the fourth successive opinion poll showed voters warming to Prime Minister Gordon Brown.

Conservative leader David Cameron, pointing to the U.S. Congress's rejection of a $700 billion bank bailout plan, said in an unscheduled speech at his party's annual conference that he was ready to set aside party differences to help Brown.

"Let us not allow the political wrangling that took place in America to happen here in our own country," Cameron told party activists in England's second city, Birmingham.

Brown's standing has jumped since he pledged, in his speech at the ruling Labour Party's annual conference last week, to do whatever was needed to ensure financial market stability and to protect those hardest hit by the crisis.

Polls show that voters still prefer Cameron to Brown -- but that in a crisis they would rather have Brown, the seasoned former finance minister who took over from Tony Blair last year.

A poll published in the Independent newspaper on Tuesday showed that 43 percent of voters trusted Brown to deal with a crisis and handle the economy, against 33 percent backing Cameron.

Labour now lags the Conservatives by about 10 points, suggesting the government would be ousted in an election, but all four polls released since the prime minister spoke last week show the Conservative lead has halved.

Brown does not have to call an election until mid-2010 and will hope his handling of the financial crisis, followed perhaps by an economic recovery, will give Labour a chance of winning an unprecedented fourth term.

Cameron said the Conservatives would support the swift passage of a law confirming the central bank's powers to rescue failed banks, dropping a minor objection that might have delayed progress.

But finance minister Alistair Darling appeared to rebuff Cameron's approach, telling reporters after meeting Brown and Bank of England Governor Mervyn King that he already had the powers he needed to stabilise the situation.

"The governor of the Bank of England, myself and the Financial Services Authority will do whatever is required to maintain stability and to protect the interests of depositors," he said. "I already have taken the powers that I need."

The government has stepped in twice this year to nationalise mortgage lenders hit by the credit crunch. Bradford & Bingley was taken into public ownership last weekend and Northern Rock was rescued by the government in February.

(Editing by Tim Pearce) Keywords: BRITAIN CONSERVATIVES/

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