LONDON (Reuters) - Britons cut back on trips and spending abroad at the end of last year as the weakening pound and credit crunch took their toll, but their decision to stay at home could provide a welcome boost to Britain's ailing economy.

Official data yesterday showed trips abroad by UK citizens fell six percent in the three months to November to 16.4 million, with spending down six percent to £8.7 billion.

A rapidly weakening economy and sharp cuts in interest rates have driven the pound down more than 20 percent against the euro in the last year and the currency has lost nearly 30 percent against the US dollar from its peak of above $2.

Sterling's decline has made holidays in destinations like Spain, France and Italy vastly more expensive for cash-strapped Britons, already hit hard by huge rises in energy prices last year and worried about their jobs as unemployment rises.

Airlines have been slashing prices to encourage people to book vacations, although tour operators have said they expect demand to hold up well.

Still, VisitBritain, the national tourism body, reckons around one in five Britons, or some four million people, who holidayed abroad last year will stay at home in 2009, providing a significant boost to the domestic tourist industry.

It says tourism already contributes some £114 billion to the economy, or around 8.2 percent of Gross Domestic Product. And it sees scope for that growth to continue.

"The potential is there for 2009 to be a good year for British tourism both inbound and domestically," said Elliott Frisby, a spokesman for VisitBritain. "Tourism provides a real opportunity to boost and support the economy in this difficult time."

And the fall in sterling means Britain is now a much cheaper destination for overseas tourists.

That was not yet reflected in yesterday's data, which showed a five percent fall in visits to the UK by foreign tourists, although spending rose one percent.

But Frisby reckons Christmas shopping trips could have helped boost overseas tourism in December.

"If there's any benefit from the exchange rate we probably wouldn't have seen it in November as there's a lag, but we might well see it in the December figures."

"There has never been a better time to travel to Britain, it's much more affordable than in the past."