That is 25 million more than its nearest rival, the house sparrow, with the great tit in third spot and the robin and willow warbler equal fourth.
Nearly 4.5 per cent of chaffinches are in Britain - which can now boast 18 separate species - more plentiful than in any other European nation.
They are headed by the Scottish crossbill, unique to Britain with 600 breeding pairs.
To the surprise of ornithologists, there are also more wrens, blue tits, dunnocks and sparrowhawks in Britain than anywhere else in Europe.
The new figures have been compiled after years of study by an army of volunteers across the continent, including those from the British Trust for Ornithology, Scottish Ornithologists' Club and BirdWatch Ireland.