1 of 5
PA, Andrew Milligan) UNITED KINGDOM OUT NO SALES NO ARCHIVE, Associated Press
Vote Yes, and No, supporters exchange views with each other at the Grassmarket in Edinburgh during a tour by a politician ahead of the Scottish Independence referendum, Monday Sept. 8, 2014. The Member of Parliament is visiting 100 streets in 100 days making his case for a No vote in the referendum which takes place on September 18.

GLASGOW, Scotland — Spooked by recent polls, Prime Minister David Cameron and other British political leaders rushed north to Scotland on Wednesday, where Cameron begged Scots not to break his heart by voting to become independent from the United Kingdom.

Cameron's personal plea aimed to keep the 307-year-old union between England and Scotland intact and prevent himself from going down in history as the U.K. prime minister who lost Scotland. He is likely to face calls from his Conservative Party to step down if Scots vote to secede.

In a rare display of cross-party unanimity, Cameron, Labour leader Ed Miliband and Liberal Democrat chief Nick Clegg all pulled out of a weekly House of Commons question session in London to make a late campaign dash to Scotland as polls suggest the two sides are neck-and-neck ahead of the Sept. 18 independence referendum.

"I would be heartbroken ... if this family of nations is torn apart," Cameron told an invited audience at the Edinburgh headquarters of the Scottish Widows insurance firm.

Critics noted that Cameron did not risk speaking before an uninvited audience of Scots on the street.

Cameron's Conservatives are deeply unpopular in Scotland. Many independence supporters cite his government's budget-slashing policies as one reason they want to leave the United Kingdom.

Scottish nationalist leader Alex Salmond said visits by unpopular London-based politicians could only help his Yes campaign.

"If I thought they were coming by bus, I'd send the bus fare," he said.

Cameron acknowledged his unpopularity, but said the vote was not about giving "the effing Tories" a kicking.

"This is not a decision about the next five years," he said. "This is a decision about the next century."

Cameron has ordered the blue-and-white Scottish flag to be flown over his office at No. 10 Downing Street until the vote in a sign of support for Scotland's place in the union.

The close race ahead of the vote has sent shudders through the financial markets. The pound and shares in Scotland-based financial institutions have sagged amid uncertainty over what currency an independent Scotland would use and whether businesses and capital would flee across the border.

Financial group Standard Life added to the jitters, announcing Wednesday it was ready to move parts of its business to England if Scotland votes for independence. Standard Life employs 5,000 people in Scotland and has been based there for 189 years.

In a statement to shareholders, the company said "in view of the uncertainty around Scotland's constitutional future, we have put in place precautionary measures which would help enable us to provide customers with continuity."

Those measures include transferring pensions, investments and other long-term savings to England to ensure they remain part of Britain's currency and tax regime.

Salmond's pro-independence Scottish administration argues that North Sea oil revenue, much of it in Scottish waters, will underpin the prosperity of an independent Scotland. Others say that view is based on an optimistic assessment of how much oil remains.

The chief of the oil giant BP said Wednesday that remaining reserves were "smaller and more challenging to develop than in the past."

"Future long-term investments require fiscal stability and certainty," BP CEO Bob Dudley said. "As a major investor in Scotland — now and into the future — BP believes that the future prospects for the North Sea are best served by maintaining the existing capacity and integrity of the United Kingdom."

Jill Lawless reported from London.