Unionist business leaders' fears that the Scottish referendum is stifling investment have been dismissed as excuses and scaremongering by nationalist company bosses.

Bosses from power firm Aggreko, care home firm Renaissance Care and Apex Hotels said there has been "a marked increase" in nervousness from international investors.

But these fears were dismissed by bosses from engineering firm Clyde Blowers, property investors The Klin Group and Scottish Estates and nationalist business umbrella group Business for Scotland.

For some companies independence is "being used as an excuse because their figures have dropped" while the same fears about a flight of investment were being used prior to the devolution referendum in 1997, they said.

Aggreko chief executive Rupert Soames, who employs about a tenth of his 6,500-strong UK workforce in Scotland, said: "We have noted a marked increase in the nervousness and questions that we have been getting from investors in the last six months.

"Now that the polls are getting closer, I think they are getting much more worried."

He added: "My prediction would be very rapidly banks will want to move their domicile to London as they will need the protection of the Bank of England as a lender of last resort."

Gordon MacIntyre-Kemp, chief executive of Business for Scotland, said: "I remember being told businesses were going to leave Scotland (after devolution), all the banks were going to relocate.

"People are saying the same things about the same companies. I've heard it all before.

"If businesses didn't leave after devolution, I don't think they are going to leave after independence."

Apex Hotels chairman Norman Springford, who employs about 800 people UK-wide, said: "We are a very patriotic Scottish family company, we started in Scotland, we invest in Scotland and, of course, we will continue to invest in Scotland.

"We will not relocate but we have decided as a board over the next several years we will focus our capital investment programme in London in particular.

"That is perhaps a message that others investing from outside Scotland may well be making similar decisions."

Robert Kilgour, chief executive of Renaissance Care, which employs around 650 people in Scotland, said: "Healthcare investment funds that I have used in London and abroad over the last 25 years have said that with the uncertainty over independence, the referendum and currency they are not prepared to do any projects.

"They are not saying they won't do it after the referendum post Yes or No, but they are saying that until there is certainty they are not prepared to invest.

"Certainly it has put a few projects that I have been looking at on hold for the time being.

"I'm a confident that it's a delay. These projects are going to happen but for a variety of reasons, the main one being the uncertainty, we've decided to consolidate."

But Mr Macdonald said: "We saw a report at the end of 2012 which said independence was a great problem, it was a very prominent agency who are London based, represented here, said it was undermining confidence and their figures were down.

"This year that same company have had a record year. They've no worries about independence, or at least they're not talking about them.

"I've got to interpret that as the independence issue being used an excuse because their figures have dropped."

But Mr Soames warned: "I don't think you should comfort yourself that just because investment has been very strong until recently that actually there is not a change of atmosphere.

"People are much more worried about it now in the international capital markets."