The sit-in, which lasted several hours, ended shortly before midnight when Mr Montgomery said that editorial independence at MGN would be preserved.
A mass meeting of MGN staff earlier voted overwhelmingly to record their 'disgust' at Mr Montgomery's appointment and their intention not to co-operate with him.
MGN's board narrowly approved the appointment yesterday, along with that of a new finance director, John Allwood, who was finance director of Sky Television until last year, and a new non-executive director, the Labour peer Lord Hollick.
The board moves came with a statement by John Talbot of Arthur Andersen, the accountants that control 54 per cent of the MGN shares, who said that the appointments would strengthen the group's position as an independent company. He added that this means the administrators are unlikely to sell the 54 per cent holding in the near future.
At a stormy board meeting yesterday, three directors, including the chairman, Sir Robert Clark, voted in favour of the appointment, while two opposed Mr Montgomery's appointment and two abstained. Vic Horwood, the current chief executive, was believed to be among the opponents.
Joe Haines, the former press secretary to Harold Wilson, resigned from MGN's board on Thursday night in protest at the appointment, and did not attend the board meeting. Bernard Tominey, the group's operations director, has also resigned and is 'pursuing other interests'.
The National Union of Journalists argued that Mr Montgomery's appointment would not only endanger the Labour-supporting position of the Daily Mirror, but also journalists' jobs.
'His style of editorship, learnt while editing (Rupert) Murdoch newspapers, is entirely hostile to everything the Daily Mirror stands for,' the NUJ said.
Mr Montgomery, who edited Today and the News of the World for News International, said he would maintain the left-of-centre stance of MGN's newspapers.Reuse content