A woman is seen at a window on the Royal Mile in Edinburgh, Scotland September 9, 2014. The referendum on Scottish independence will take place on September 18, when Scotland will vote whether or not to end the 307-year-old union with the rest of the United Kingdom. [Photo/Agencies]

LONDON - British Prime Minister David Cameron is making last-ditch efforts to campaign for a "No" vote in Scotland's independence referendum after the latest polls put the "Yes" and "No" sides neck and neck.

In an article published Tuesday on the website of the Daily Mail newspaper, Cameron warned against independence, saying it was a "leap into the dark."

"The United Kingdom (UK) is a precious and special country. That is what is at stake. So let no one in Scotland be in any doubt: we desperately want you to stay; we do not want this family of nations to be ripped apart," Cameron wrote.

"If the UK breaks apart, it breaks apart forever. So the choice for you is clear: a leap into the dark with a Yes vote, or a brighter future for Scotland by voting No," he added.

The article was published ahead of Cameron's trip to Scotland Wednesday, joined by Labor Party leader Ed Miliband and Deputy Prime Minister Nick Clegg, leader of the Liberal Democratic Party, to campaign for the Better Together Union.

All three leaders will miss Prime Minister's Questions on Wednesday, amid indications in polls that Scottish voters could vote to leave Britain in the Sept 18 referendum.

In October 2012, Cameron and Scottish First Minister Alex Salmond signed the Edinburgh Agreement, allowing Scotland to hold an independence referendum in autumn 2014 on the question "Should Scotland be an independent country?"

On Sunday, the published YouGov Plc's survey for the Sunday Times put the "Yes" voters ahead of the "No" voters for the first time by 51 percent against 49 percent.

On Tuesday morning, a TNS poll put the "Yes" and "No" campaigns equal on 41 percent, backing for the "Yes" campaign was up from 38 percent last month, while support for maintaining the union had dropped from 46 percent.

Cameron said that the three leaders, while in Scotland, will have their own ways, separately, of talking about why it is better together in the union, reiterating that "it's a matter for people in Scotland to decide, but we want you to stay."

Meanwhile, Salmond said that it had been the day that the "No" campaign "fell apart at the seams."

He maintained that the polls at the weekend, which caused so much panic in the "No" campaign, actually showed that independence was the most popular option.

As the referendum to decide the destiny of the 307-year union is approaching, uncertainties remain over the future of Scotland and the rest of the UK.

Following an independence vote, Britain and Scotland would face 18 months of talks on issues such as what money Scots would use, whether an independent Scotland would be allowed to remain a member of the European Union as well as how to split British public debt and North Sea oil revenue.

Among them, the currency question is the most thorney issue which could exert negative influence on the British economy. While independence leaders say they will continue to use the British pound, politicians in London have ruled out a currency union.

As the result of the 18-month separation talks would affect the value of the pound, foreign investors in Britain could delay big decisions -- opening a factory or hiring new staff -- until a time when they can better gauge the risks and costs.

Investment bank Goldman Sachs last week warned that the consequences of a "Yes" vote for the Scottish and the British economies could be "severely negative."

In fact, increased worries that Scotland could separate from the United Kingdom had kept pressure on the pound Tuesday.

Ultimately the currency held steady for the day, but only after rocky trade pushed it to 1.6065 U.S. dollars, its lowest level against the greenback since November last year.