THE decision to open secret Government files on Arthur Donaldson, a

founder of the Scottish National Party, who was interned during the war,

was condemned yesterday by SNP vice-president Gordon Wilson.

Documents which disclose that MI5 was behind covert action against

Scottish nationalist organisations during the last war were made public

this week.

It has also emerged, in further close examination of the files by The

Herald, that Scottish poet Hugh MacDiarmid came under the scrutiny of

MI5 and that letters written by him were intercepted and kept on

intelligence files.

The file on the 1941 operation -- which became a cause celebre --

contains a confidential Crown Office report which claims Mr Donaldson

had used the home-rule movement as a cloak for subversive activities.

Raids on his home and those of his associates were made, according to

the documents, because of ''grave'' suspicions attached to Mr Donaldson

against whom it claimed there was ''a considerable body of evidence

demonstrating highly subversive activities over a long period.''

Mr Wilson said it was ''completely disgraceful'' for the Scottish

Office to release the records when Mr Donaldson, a former chairman of

the party who died last year aged 91, was unable to repudiate the slurs.

Mr Wilson said: ''Arthur Donaldson always maintained he did not know

why they had picked him up. He pressed for the release of these files

for many years. He would have been first into the courts to sue to

defend his reputation.''

The Donaldson files disclose that the operation was instigated by the

intelligence services, run in Scotland by MI5 Major P. Perfect, assisted

by Richard Brooman-White, who went on to become Tory MP for Rutherglen

and an Under Secretary at the Scottish Office.

The file claims raids on houses all over Scotland uncovered evidence

of links with the Nazis. A letter to a Nazi agent, Dr Von Teffenar, was

found at the home of R. E. Muirhead, a senior figure in the movement.

The Secretary of State for Scotland claims in a letter on the file to

have ordered Mr Donaldson's release five weeks after his internment.

A hand-written note on the file by a civil servant, states:

''Donaldson was released from interim detention because MI5 would not

allow essential witnesses to give evidence before the Advisory Committee

which might have led to disclosure of their identity.''

This appears to give credence to the belief that MI5 had infiltrated

the ranks of the home-rule movement.