The campaign for Scottish independence from the U.K. has taken the lead in an opinion poll for the first time since the referendum campaign began in earnest.

According to a YouGov survey conducted on behalf of U.K. newspaper the Sunday Times (subscription) said that the nationalist "yes" camp has the support of 51 percent of voters, compared to the unionist "no" camp's 49 percent. If accurate, the unionists will have lost a 22 percentage point lead in the space of one month, the paper says.

The poll was taken between Sept. 2 and 5, and consisted of interviews with 1,084 people.

Nicola Sturgeon, deputy first minister of Scotland's devolved government and deputy leader of the nationalist Scottish National Party, said that the poll showed that the yes campaign was gathering steam, according to a report from BBC News

"This breakthrough poll shows that yes has the big momentum. More and more people are beginning to realize that a yes vote is Scotland's one opportunity to make [the country's] enormous wealth work better for everybody who lives here.”

The Times also reported that Queen Elizabeth II, though officially neutral on the subject of the referendum, was a unionist, adding, “There is a great deal of concern” in the palace at the prospect of Scotland becoming independent.

A yes vote for independence would raise a raft of awkward issues to be dealt with by the monarch, and the U.K. government. The Queen is Scotland's head of state, and swore a vow when she was crowned to defend the U.K.'s established Anglican church in Scotland.

The yes campaign say that they would retain the Queen as monarch, as long as the voters of Scotland wished to remain a monarchy.

The other thorny issue is what currency an independent Scotland would use. Independence campaigners have said that they will continue to use the U.K. pound, but the main political parties in Westminster have ruled out any currency union with an independent Scotland. 

There is also a contentious debate as to what would happen with Scotland's membership of the European Union. Unionist campaigners have speculated that an independent Scotland my be blocked from joining the EU, but countries such as Spain or France, that have regions with long-established separatist aspirations.

The referendum takes place on Sep 18.