Deer numbers have returned to levels not seen in Britain since the Norman conquest, a new report has claimed.

And so many are roaming the countryside they are fast becoming a menace, a Government study has warned.

Herds are a hugely popular sight on Exmoor and the Quantocks in Somerset, along with numerous country parks across the West.

But scientists at Natural England say they are munching their way through undergrowth in woodland habitats, threatening rare native species like nightingales, dormice and bluebells.

Deer were hunted to the edge of extinction in the 18th century, but numbers have bounced back to two million after the introduction of species like muntjac, fallow and Chinese water deer that are smaller and breed faster.

Warmer winters, no natural predators, a fall in the number of people hunting and year-round crops mean numbers of native roe and red deer have also increased

New research presented to the British Ecological Society found in certain areas of the country the problem is so bad widespread culling may have to be introduced.

Dr Emma Goldberg, of Natural England, looked at the impact of deer in 80 protected Sites of Special Scientific Interest (SSSIs).

She said deer browse out the undergrowth such as thickets of brambles and honeysuckle that birds nest in.

The increasingly bare woodland floor can also impact on other mammals like dormice and insects like butterflies.

“The ecological knock-on impact is that it can have a direct impact on those shrubs, such as hazel, privet and some of the rarer shrubs, which may get browsed out of the woodland altogether,” she said.

“This has yet another knock-on impact for other species, like dormice or ground-nesting birds. Even butterflies can be affected because the shrub layer provides an important nectar source.”

Ultimately, she said the deer threaten the woods themselves.

In the countryside a major concern about deer is the spread of cattle disease like bovine tuberculosis and foot-and-mouth.

The National Deer Vehicle Collisions Project also estimates there are 74,000 accidents caused by deer every year, 44 per cent are in urban areas.

The Deer Initiative, which is a partnership between the Government, private sector and charities, is now working with landowners to carry out culls in those areas by trapping and shooting.

The initiative’s Peter Watson admitted that councils and charities are reluctant at first because of concerns about animal welfare.

But he said the wildlife trusts, RSPB and Woodland Trust are all part of the initiative as they realise the deer population must be controlled for the good of wildlife.

Currently around 350,000 deer are killed every year, mostly by rifle, but it could be increased to 500,000. Trained hunters carry out the culls and the venison is then sold.

However many animal rights groups argue that deer are now a part of the urban and rural landscape like foxes that should be welcomed.

They insist that the animals can be stopped from causing a nuisance through control measures like contraception, relocation, ‘deer passes’ over motorways and fencing.