A former chief executive of the Scotch Whisky Association has complained of intimidation from senior SNP members and claimed other business leaders have suffered such pressure during the referendum campaign.

Gavin Hewitt said challenges to the Scottish Government's views on independence were regrettably rebuffed too often by dismissal of the messenger. "Sometimes it goes as far as intimidating calls from senior SNP members," he said. "That is not a good basis on which the electorate should decide Scotland's future on September 18."

He stressed the intimidation directed at him by Nationalists had not been in the context of the independence referendum, but he said: "I do know people who have had calls in the context of the independence debate. But for obvious reasons I'm not going to indicate who. It does go on unfortunately."

Mr Hewitt said intimidation by the SNP had been "prevalent" but business people were not ­willing to talk about it, adding: "The message was - get out of this debate."

He said the emails from SNP special advisor Campbell Gunn about carer Clare Lally "amount to that sort of thing."

Scottish Secretary Alistair Carmichael said he talked to ­business leaders all the time and they told him independence would be bad for their firms but it would also be "bad for their businesses to get on the wrong side of the Scottish Government". He claimed: "The Campbell Gunn intervention is entirely consistent with that pattern."

Last night, an SNP spokesman said in response: "We encourage every single person to get involved in the referendum debate if they wish to - it is a fantastic opportunity for Scotland - and there are vigorous contributions from business people and others virtually on a daily basis which receive widespread attention.

"Some of these are opposed to independence and some are for; for example, the pro-Yes Business for Scotland organisation, which has some 2000 members.

"We have no knowledge of the calls to which Mr Hewitt refers and would urge him to participate in the debate if he wants to, just as he is a very vocal opponent of minimum pricing for alcohol."