A vote for Britain to leave the European Union would be "deeply felt" and could lead to the EU breaking up entirely, Sweden's foreign minister has warned. Margaret Wallstrom said other member states might decide to hold referendums or demand "special treatment."

Even if the UK decides to stay, she told the BBC it "might also lead to other countries saying: 'Well, they negotiated, they asked and demanded to have a special treatment, so why shouldn't we?'"

She added that the "spill-over effect will be unfortunately felt, deeply felt. It would be bad either way."

If Britain decides to leave on 23 June, she said it might lead to other EU member states calling for their own referendums on whether membership still suited them.

Her comments came after a survey of 2,000 people by ORB for The Independent found that 55% of people believe the UK should leave the union, while 45% believe they should remain.

The result is sure to heighten fears that the remain campaign is losing ground, particularly among Labour supporters as the poll found that 44% of those who voted for the party in the last election, now want to leave the EU.

Despite the seemingly growing support, 17 major house builders joined the chorus of businesses that have called on the UK to remain. An open letter signed by companies and housing associations - including Barratt Homes, the Berkeley Group and Peabody - said leaving the EU was "the last thing Britain's developers and house builders need".

"We are developers and house builders working throughout the country to build more, much needed, housing to ensure millions of people can fulfill their dream of buying their own home," they said.

"What any developer requires is confidence and continued support from their financial investors - and those investors need certainty over wider market conditions," they added. "There is now a clear consensus that a vote to leave will create considerable uncertainty for Britain. Investment will suffer as confidence in the economy wavers. That is the last thing Britain's developers and house-builders need.