Wild boars could spread through ''the whole country'' by swimming miles across its longest river, an expert claims - writes Paul Andrews.

Dr John Dutton says the feral pigs could easily start to move around the UK by taking to the River Severn.

The centre of England and Wales' boar population is currently the Forest of Dean.

Numbers there have boomed and there are reports of dogs, cats and people being attacked, with one man having had his finger bitten off by a boar.

The animals have also learned to go into towns on rubbish collection days to look for food.

Dr Dutton says the boars could spread as they are good swimmers.

University lecturer Dr Dutton says the Forest of Dean provides boars with ideal territory to breed in.

The University of Worcester senior ecology lecturer said the wild boar would easily travel to farms or woodlands across the river looking for food or to escape threats.

He said: "Potentially if we didn't do anything and there was anything else to prevent them such as major roads or rivers, then they could reoccupy the whole country.

"I'm not sure that would happen in any short time.

''After all, they have been in the Forest now for 20 plus years almost and therefore they are going to expand solely in different directions.

"But the River Severn, certainly north of Gloucester, would not stop them crossing if they felt like it because it is not a particularly large river and they are very good at swimming."

Dr Dutton has carried out research into the reintroduction of wild breeds such as boar and beavers in the Forest of Dean.

In parts of Europe there have been reports of boar attacking people after emerging from rivers and the sea.