Prime Minister David Cameron rejected on Wednesday a proposal by the Scottish National Party (SNP) that the United Kingdom should only quit the European Union after a future referendum if a majority in each of its four constituent parts vote to do so.
Cameron has promised a referendum in 2017 on the UK's continued EU membership if his Conservative Party, which has grown increasingly Eurosceptical, wins a 2015 national election.
Incoming SNP leader Nicola Sturgeon said earlier on Wednesday the United Kingdom's EU exit should only go ahead if approved by a majority in Scotland, Wales and Northern Ireland as well as in England, home to 85 percent of the UK population.
"We are one United Kingdom. There will be one in/out referendum (for the EU) and that will be decided on a majority of those who vote. That is how the rules should work," Cameron told the UK parliament in response to Sturgeon's proposal.
Scotland, Wales and Northern Ireland have varying degrees of autonomy but the British government in London controls foreign policy and is not legally required to consult the regional administrations over issues such as EU membership.
Cameron has adopted an increasingly critical stance on the EU as he tries to fend off an electoral challenge from the United Kingdom Independence Party (UKIP), which wants to quit the bloc. He says he wants Britain to stay in a reformed EU.
Scots, who last month rejected independence in a historic referendum, are more likely to back EU membership than the English, polls show. The SNP has said the UK's exit from the 28-nation bloc could put Scottish independence back on the agenda.
In a speech on Wednesday evening, Sturgeon is due to flesh out her proposal, which seeks to protect Scotland, with just five million of the UK's 64 million people, from being forced to leave the EU against its own wishes.
"This proposal transforms the terms of the UK debate on Europe - which so far has been all about the Westminster parties dancing to UKIP's tune," she will say in Edinburgh, according to advance extracts from her speech.