LONDON (Reuters) - Britain's worst recession in more than 50 years will soon be confirmed as over, if economists' forecasts for fourth-quarter GDP data due today are right, but the strength of any recovery looks less certain.

Britain entered recession in the second quarter of 2008 and is the only one of the Group of Seven nations officially to remain there after output bucked expectations and continued to shrink in the third quarter of last year.

Any growth will be a relief to Prime Minister Gordon Brown, whose Labour Party is significantly trailing the opposition Conservatives in the run-up to a national election due by June.

But whether it will be enough to shift public opinion remains to be seen.

"I am confident that the UK economy is emerging from recession but there are dangerous global forces ... which means that the world and the UK economy remain fragile and policymakers around the world and the United Kingdom must remain vigilant," Brown told a news conference yesterday.

Economists predict on average that Britain's economy grew by 0.4 percent from October to December, with none of the 35 polled by Reuters seeing a negative reading — though that was also the case before the Q3 shock.

However, this time a return to growth requires less of a turn-around in output, because a contraction of just 0.2 percent was recorded for the third quarter compared to 0.7 percent in the second.