Uncertainty over the Scottish government's plan to hold a referendum on independence from London is damaging investment in Scotland, chancellor George Osborne said Sunday.

In May, the pro-independence Scottish National Party (SNP) won a majority in the devolved parliament and pledged to hold a referendum on independence within five years, some 300 years after England and Scotland were unified.

Scotland's First Minister Alex Salmond has said the referendum will be held in the second half of his government's five-year term, but the exact date and the question to be put to Scottish voters have not yet been decided.

The uncertainty about independence, the uncertainty about what sort of referendum Alex Salmond wants, the complexity of the question that he wants to pose to the Scottish people, all those things -- at a time when anyway there is a lot of economic uncertainty in the world -- are adding to the economic uncertainty in Scotland, Osborne told the BBC.

There are major businesses around the world who have asked me ... in the last year: 'Tell us what is going on in Scotland. We are worried about making an investment in that country', Osborne said, in comments that may signal the British government plans to take a more combative approach on the question of Scottish independence.

I've told them 'go ahead with the investment' but I have to say those questions are being asked and I think that is having a direct impact on Scottish jobs and Scottish prosperity, Osborne said.

When pressed, he declined to say which companies had raised the issue, but said they are some of the largest companies in the world.

A poll published last month found support in Scotland for the SNP's plans had surged, with 49 percent backing independence and 37 percent opposed.

All Britain's major political parties including the Conservatives and Liberal Democrats who make up London's coalition government are opposed to the break-up of the union.

A spokesman for Salmond said Osborne's comments were another example of the Conservatives talking Scotland down.

It was the height of hypocrisy from the chancellor (finance minister) of a government which is undermining Scotland's recovery and has caused massive uncertainty to our vital offshore oil and gas industry with a shock tax hike, he said, referring to the coalition's surprise move in March to raise a tax on North Sea oil and gas output.

International companies are investing in Scotland because of the business friendly environment the Scottish government is putting in place, he said.

(Reporting by Adrian Croft)