Britain has 'masses of space' and the issue of immigration is 'not very important', a senior member of the independent economic watchdog has claimed.

Stephen Nickell, a board member of the Office for Budget Responsibility, said just 10 per cent of the country has been 'urbanised'.

And he warned the NHS would be in 'dire straits' without the influx of migrant workers to take jobs.

Stephen Nickell, a member of the Office for Budget Responsibility board, told MPs that there is 'plenty of space' in Britain

Latest figures show that net migration is rising, with 260,000 more people arriving in the UK in the year to June than left.

The issue is set to dominate next year's general election campaign, with all the parties promising to act on curbing benefits which can act as a 'pull factor' to attract EU nationals to Britain.

The urbanised part of Surrey occupies less of Surrey than golf courses. So in some senses, plenty of space

But Mr Nickell told MPs that while new arrivals had held down unskilled wages 'to some extent' but the overall impact was marginal.

The former economics professor at Oxford university and the London School of Economics was giving evidence to the Treasury Select Committee.

Mr Nickell said: 'It's perfectly true, I think, from the evidence that the pay of unskilled workers, particularly in the service sector, has been held back to some extent - not a massive extent, but to some extent - by unskilled immigration...

'At the end of the day - let's say over the next 10 years or so - the general consensus is that for the native population, the existing population, immigration may be a little bit good, it may be a little bit bad economically. But there isn't overall that much in it.'

Giving evidence to the Treasury select committee, Mr Nickell warned the NHS would be in 'dire straits' with migrant workers

But he stressed that the NHS can only survive with migrant workers. 'Obviously there are special situations like in the health service, for example - some 35 per cent of health professional are migrants.

'It's quite plain that, if they weren't there, the health service would be in absolutely dire straits.'

Last month Witold Sobków, the Polish ambassador to the UK, revealed plans were being drawn up to persuade hundreds of health staff trained in Poland to return home, declaring: ‘We want them back.’

Some 35 per cent of health professional are migrants... if they weren't there, the health service would be in absolutely dire straits

David Cameron has pledged to work with other EU countries to reduce migration across the continent, warning public services in Britain are struggling to cope with rising populations.

But Mr Nickell suggested that large parts of the country are far from full, and able to cope with more new arrivals.

He said the argument about immigration, 'basically boils down to people, the number of people'.

'The evidence suggests that, since more immigrants mean more housing, more roads, more airports, more incinerators, more more more of this being required.

'And since the evidence would suggest that people by and large don't like these things - especially if they are near them - I think that is the key issue about immigration that people may wish to face up to.'

Mr Nickell went on: 'One argument says 'We are a small island, not much room'.

'On the other hand, of course - there is masses of room. The urbanised part of Britain occupies less than 10 per cent of the surface area.

'The urbanised part of Surrey occupies less of Surrey than golf courses. So in some senses, plenty of space.

'But as you know, explaining the situation ... there's plenty of room, these issues are really not very important, it doesn't get you very far. This is not the way people think about these things.

'People think about these things on the basis of their experience and what they read in the newspapers.

'Most of the things that people object to arise because there are just more people.'

Fears over immigration have been widely credited with fuelling the recent surge in support for Ukip, which saw the party top European polls and win two Commons by-elections.

Before the last election, Mr Cameron pledged to reduce net annual immigration below 100,000 by the general election, but figures released last month showed it is running at 260,000.