London\'s Heathrow is falling behind rival European airports in the battle for lucrative routes to China because of the constraints on growth at Britain\'s largest airport, operator BAA said yesterday. BAA, which was prevented by the UK government from building a third runway at Heathrow because of environmental concerns, said passenger traffic at its British airports edged up last month with Heathrow enjoying its busiest ever January despite a slight fall in traffic to China. \"Heathrow\'s China traffic in January, including Hong Kong, was down by 0.7 per cent versus the previous year. Through 2011 as a whole, Heathrow\'s China traffic was up 3 per cent versus 2010,\" Chief Executive Colin Matthews said. \"This growth rate was well short of the growth generated by other European hubs, with Paris and Frankfurt growing at 9 per cent versus 2010 and Amsterdam growing at 6 per cent.\" Matthews added that the trend showed that capacity constraints at Heathrow, Europe\'s busiest airport, were \"damaging the UK economy when the country can least afford it.\" Full capacity Heathrow is operating at full capacity after Britain\'s Conservative-led coalition government blocked development of a third runway when it came to power in 2010 as further expansion of the west London site would mean a huge increase in the number of planes flying directly over the capital. London Mayor Boris Johnson has instead proposed building a new London hub airport in the Thames estuary. There were 476,197 flights at Heathrow in 2011, representing 99.2 per cent of the airport\'s limit.