Lord Forsyth of Drumlean, the peer who made the accusations, said no-one in the First Minister’s office had said they were untrue.
The former Tory Scottish secretary also said that he had received confirmation of the alleged threats to Mr Osborne, the Chancellor, in the last week.
He told The Herald: “I was told by someone very senior that Salmond threatened to boycott the referendum. He had a conversation with the Chancellor.
“Last week I asked the Chancellor if it was correct that Alex Salmond refused to co-operate and he said it was. No-one from the First Minister’s office has denied this. They simply say they don’t know where this has come from.”
He added that Scots were entitled to know what Mr Salmond’s intentions were.
The row centres on Westminster’s ability to call a separate independence referendum of its own.
Coalition ministers have not ruled out calling their own poll.
But Scottish ministers insist that only the Scottish Government has a proper mandate to ask the Scottish people about leaving the rest of the UK.
Lord Forsyth triggered the controversy on Monday.
During question time in the House of Lords he asked the Coalition Government to confirm that Mr Salmond had privately told them that he would “make it his business to boycott that referendum and prevent the police and other services from seeing it carried out”.
In response to the accusations, the First Minister’s office released a statement saying: “We have no idea what Lord Forsyth is talking about.”
Last night a spokesman for Mr Salmond said: “I have nothing to add to what was said yesterday.
“We have given our response on the matter.
“What the First Minister has said is that a referendum is clearly a matter for the Scottish Government and the Scottish Parliament.”
A spokesman for Mr Osborne said last night: “We don’t comment on private conversations.”