Scotland's interests are being routinely forgotten, ignored and dismissed by Whitehall officials when they seek to influence policy and law-making in Brussels, according to a leaked government report.

The confidential advice from the Scottish Executive's top official in its European office to Jack McConnell says officials overwhelmingly feel devolved institutions are being held back in getting their point across where it matters in European institutions.

In unusually blunt terms, Michael Aron tells the First Minister that the Scottish administration is sometimes deliberately excluded, and that the consequences can be "disastrous".

More often, Whitehall is defensive about its European policy and frustrates Edinburgh by keeping ministers and officials "out of the loop". It is "not uncommon" for the executive's views to be ignored by Whitehall.

The report, which has been leaked to The Herald, cites examples of ministers being frozen out of council meetings, and humiliated by having to sit in another room where they can only listen to discussions. Information is shared by Edinburgh but without reciprocation from Whitehall, and officials in Edinburgh are only told about vital meetings in London when it is too late to arrange travel and attend.

The executive's access to the powerful group of commissioners in Brussels is largely controlled by the Foreign Office, on condition Scotland argues the UK line. In drawing up regulations on spirit drinks, where Edinburgh was pushing the interests of the Scotch whisky industry, the report says the UK government insisted on arguing the opposite case.

The head of the executive's Brussels office recommends in his report to the First Minister and Scottish cabinet that he should move to lobby the commission directly instead of being "constrained" by having to go through Whitehall.

In a damaging reference to the role of Scotland Secretary Douglas Alexander, Mr Aron, who was a senior UK official in Brussels until last year, accuses the Scotland Office of failing to argue for Scottish interests in Downing Street cabinet. "The diminishing role of the Secretary of State for Scotland has meant that there is no longer a hard-hitting voice within cabinet meetings speaking out on behalf of Scottish interests," his report states. "This is a blow to a number of policy areas, but especially fisheries policy where the Scottish position is different to that of the rest of the UK."

The report, written last September, reflects on questionnaire feedback and interviews with executive officials. "It hasn't been uncommon for Whitehall to dismiss views of the executive when formulating the UK line," Mr Aron wrote. "The most common complaint is that Whitehall tends to forget about consulting the executive. It can have a disastrous impact on executive policy."

The Scottish National Party last night described the report as "devastating, proving everything that the SNP has ever said about Scottish misrepresentation in Europe under the executive".

Angus Robertson, the party's foreign affairs spokesman, said: "Whitehall departments totally ignore the Scottish Executive, and Scotland's interests across the board suffer."

He said it was "appalling and insulting" that Scottish ministers have to listen to the Council of Ministers debate decisions from outside the meeting room.