LONDON, FEB 13 - British airport operator BAA said capacity constraints at London's Heathrow airport led to a fall in passenger traffic to China last month with competing European hubs picking up the slack.

The owner of Heathrow -- Europe's busiest hub -- on Monday said passenger traffic at its airports edged up last month with Heathrow enjoying its busiest January ever despite a slowdown in traffic to China from London.

Heathrow's China traffic in January, including Hong Kong, was down by 0.7 percent versus the previous year. Through 2011 as a whole, Heathrow's China traffic was up 3 percent versus 2010, Colin Matthews, BAA's Chief Executive said.

This growth rate was well short of the growth rates generated by other European hubs, with Paris and Frankfurt growing at 9 percent versus 2010 and Amsterdam growing at 6 percent.

Matthews added that this trend showed that capacity constraints at Heathrow were damaging the UK economy today when the country can least afford it.

Heathrow airport is operating at full capacity after plans to build a third runway there were scrapped by Britain's coalition government when it came to power in 2010.

There were 476,197 flights at Heathrow in 2011, representing 99.2 percent of the airport's limit. Paris and Frankfurt airports now have 1,000 more flights each year to the three biggest Chinese cities than London does.

Earlier this month a report by business group London First said Britain should consider all options for increasing capacity at Heathrow, including a third runway and allowing planes to land and take-off simultaneously on its two runways.

The report, which criticised the government for ruling out a third runway at Heathrow for political reasons, said all viable options for meeting the UK's long-term need for further airport capacity, including a new airport, should be considered.

BAA owns London's Heathrow as well as Southampton and Stansted in England, plus Glasgow, Edinburgh and Aberdeen airports in Scotland.

BAA -- majority owned by Spanish infrastructure group Ferrovial -- said it handled 7.5 million passengers in January, up 0.5 percent.

Heathrow served 5.2 million passengers last month, a record for January and up 2.3 percent on the same month last year, BAA said.

The operator must sell London Stansted airport, Britain's fourth busiest, after a court dismissed its appeal against a ruling by the UK's competition watchdog earlier this month.

Ferrovial shares in Madrid were flat at 9.48 euros by 0805 GMT.

(Reporting by Rhys Jones; editing by Sarah Young)