Business leaders in Scotland are unwilling to question Alex Salmond's independence drive because of the "bile and ire" they receive, the boss of one of the country's most successful firms warned tonight.

Rupert Soames, chief executive of power generator giant Aggreko, dismissed the benefits of breaking away from the UK as "small and tenuous" compared to the "large and serious" disadvantages.

But he said many of his associates avoided attacking the idea in public even though they harboured the same concerns.

Giving evidence to the Lords Economic Affairs Committee, Mr Soames - grandson of Winston Churchill - said: "Over the past couple of years anyone who has dared open their mouths on the subject with views that are contrary to those of the SNP have brought down on themselves rains of bile and ire which are really very unpleasant.

"A lot of the language is very intimidatory. I bluntly think that people think they have got better things to do than be hauled over the coals.I think that process will begin to change as we get closer to the referendum."

Mr Soames said Glasgow-based Aggreko would face "enormous additional complexity" from independence in the short-term, and there was likely to be a permanent burden.

"As far as Aggreko is concerned I can say very simply that our view and my view of what the impact would be on our business of independence is that the advantages would be small, tenuous and unlikely to arise, and the disadvantages would be large, serious and likely to arise," he said.

"It would in the short term undoubtedly produce a great deal of business disruption...

"We would have to commit significant amounts of resources to managing whatever comes out."

He added: "I have never had a friend who has come along to me and said their divorce ended up being easier than they thought it would be."

Mr Soames said he would be nervous about having such a large proportion of his company's operations based in a country where the economy was "hugely dependent on hydrocarbons".

He suggested the worries were not just about North Sea oil stocks, but "the fact that it could be very volatile".

Mr Soames said he believed other business leaders he knew in Scotland would agree with what he was saying.

"More people will get braver about saying really what they do think," he added. "At the moment you say this is a risky enterprise, you are accused of saying you don't have any confidence in the Scottish people... it is tosh."

He went on: "Pushing it under that table saying it is going to be easy is not a very grown up way of addressing the issue."