UK Chancellor Alistair Darling will downgrade the 2009 economic outlook when he presents his pre-budget report next month but still point to growth resuming at the turn of the year as he predicted in April.

Treasury sources told Reuters that the unexpectedly rapid fall in output in the first quarter of the year meant that the economy would probably shrink by around 4.75 per cent, instead of the 3.5 per cent decline pencilled in at the time the budget was made.

The British economy has now declined for six successive quarters, marking the longest recession in at least 50 years and lagging behind many other major economies that have already started growing again.

But Treasury sources are cautiously confident that growth will resume around the turn of the year, pointing to recent survey evidence from the Confederation of British Industry and official retail sales data for October.

"The assumption is that the economy grew between 0.2 (percent) and 0.4 per cent in Q4," one Treasury source said.

Treasury sources indicated that Mr Darling would likely stick to his forecast for economic growth of one per cent to 1.5 per cent in 2010 as most forecasters were somewhere in the middle of that range, having predicted much lower outturns in April.