European Commission president José Manuel Barroso said Thursday that regions that secede from European member states would have to reapply for membership and ultimately carry the single currency.

“A new state, if it wants to join the EU, has to apply to become a member of the EU, like any state,” Barroso said on BBC radio. He added that all existing member states have to give their consent before a country can join.

Scottish nationalists, who plan to call a referendum on secession in 2014, insist that the region can remain part of the European Union. An exit, if only temporarily, could be hugely detrimental to Scottish businesses who would be locked out of the bloc’s single market.

Scotland’s ruling nationalist party planned to continue to use Britain’s sterling currency post secession to enable companies to operate with ease across the border. As a independent European Union member state, however, it would have to commit to ultimately adopting the euro from which only Britain and Denmark are exempt by treaty.

The prospect of having to leave the European Union and adopt the single currency as a condition for rejoining could further decrease popular support for Scottish secession from the United Kingdom. Although some 70 percent of the Scots wants to have a referendum, just 40 percent favored independence before Barroso made his statement on Thursday, according to opinion polls.

Scottish separatists are able to rally opposition to what they perceive as the unjust distribution of North Sea oil and gas revenues. While drilling platforms are situated off Scotland’s North Sea shore, the central government issues licenses and collects taxes. However, the value of these revenues corresponds roughly to the subsidies Scotland receives from London every year.

Opponents of independence argue that the region is economically stronger as part of the United Kingdom and exerts more influence internationally than it could separately.

After the Greater London area and Southeast England, Scotland enjoys the highest gross domestic product per capita rate in the United Kingdom. Its relatively high levels of public spending may be difficult to sustain without subsidies from London in the long term.

Under the 1998 Scotland Act, the parliament in Westminster “reserved” the power to decide over the constitutional future of Scotland. The government has temporarily delegated that authority to Edinburgh for a referendum to take place.

England and Scotland were unified in 1603 when the Scottish king James I assumed the English throne. The two countries’ parliaments were unified about a century later by the Acts of Union in 1707.