Britain could become the first major economy to tighten monetary policy since the 2008 financial crisis, Bank of England governor Mark Carney has signalled, sending sterling shooting towards a five-year high against the dollar yesterday.

British government bond yields soared, construction stocks tumbled and interest rate futures priced in a first increase by December after Carney said rates could rise sooner than markets had thought - his most hawkish comment to date.

Meanwhile, rating's agency Standard & Poor's upgraded its outlook for Britain's triple-A credit rating to stable from negative, although rivals Moody's and Fitch have still kept it a notch below triple-A.

"There's already great speculation about the exact timing of the first rate increase and this decision is becoming more balanced," Carney said in a speech alongside British Finance Minister George Osborne.

Few economists had expected rates to increase until the second quarter of next year, given the central bank's previous guidance that there was plenty of scope for Britain's economy to expand further without causing inflation.

A Reuters poll of economists yesterday showed most expect a rate rise will come by March 2015, three months earlier than a previous poll published two weeks ago. Only a minority expect a rate rise before the end of this year.

A rise in BoE rates this year would be the first since 2007 and put it ahead of both the US Federal Reserve and the European Central Bank (ECB). The Fed is still pumping extra stimulus into the US economy, while the ECB cut interest rates to record lows last week and said it may not have finished easing.

Carney said Britain's economy still had room to grow without pushing up inflation, but added that he saw little sign yet of a slowdown in the pace of expansion that the central bank had pencilled in for the second half of the year.

"The change reflects the reality in the economy. It is flying now. Employment is rising at a record pace and we see no sign of economic growth slowing from its current pace," said Rob Wood, chief UK economist at German bank Berenberg.

An interest rate rise before a national election next May could hurt perceptions of the Conservative-led coalition government by raising mortgage costs and eating into disposable income, which the opposition Labour party says is being eroded by rising prices for everything from energy to transport.

"It is absolutely without question that those people who are right on the edge at the moment will, with a small increase in interest rates, be pushed over the edge," Conservative lawmaker Mark Garnier said.

Although Britain's $2.5 trillion economy has won back the output lost in the convulsions of the 2008 crisis, Garnier said it could be a hard sell to convince voters of the recovery if they felt they had less money in their pockets.

"We can't just go to people and say: 'Yes, it's costing you more, but overall the economy is bigger'. They'll just turn around and say 'Well, it's not bigger for me'," he said.

While Britain's economy is growing fast now, its recovery began much later than in the US or Germany, and wages have fallen significantly in real terms since the financial crisis.

Carney also said the central bank would weigh carefully the merits of tackling housing market risks, including an undesirable loosening in mortgage underwriting standards, when its Financial Policy Committee meets later this month.

House prices in London have soared in the past year and though rises outside the capital have been more modest, Carney cautioned that average household debt was 140 per cent of disposable income.

Osborne said he would grant the BoE new powers to impose maximum loan-to-value and loan-to-income ratios on mortgage lending.-Reuters