All sides are due to meet again on Monday for the first substantive session of dialogue since they first sat down together two months ago. They are then expected to break for a summer recess before meeting again in September.Jeffrey Donaldson, UUP secretary, said the SDLP decision to pull out of the Forum, a consultative body of 120 members that sits separately but which has no powers, was a bitter disappointment. The Northern Ireland peace process was under new pressure last night after Unionists claimed the Social and Democratic Labour Party could have disqualified themselves from the multi-party talks. The resignation of John Hume and his 20 SDLP colleagues from the Northern Ireland Forum, in protest at the Royal Ulster Constabulary's handling of the Orange Order stand-off at Drumcree in Co Armagh earlier this month, meant they hadexcluded themselves from the Stormont negotiations, it was alleged. David Trimble's Ulster Unionist Party are to ask for a meeting with Sir Patrick Mayhew, the Secretary of State for Northern Ireland, to seek clarification of the SDLP position in future talks.

They are expected to vote overwhelmingly for action.The ballot result, due on 7 August, could be followed by a considerable escalation of the disruption on the Tube. In addition to next Monday's action, six further 24-hour walk-outs by drivers are already planned, for 7,13, 23 and 27 August and 5 and 9 September.. Perhaps the Government is behind all this, seeking to prolong the industrial action because they think they can derive some political advantage from it."As the trench warfare continued, strike ballot papers were sent to another 5,000 Underground employees - signalling, maintenance and station staff Like the drivers, they are seeking a cut in hours. Jimmy Knapp, RMT general secretary, said: "Why on earth should we call off the strike on the basis that they might 'think' about going to Acas? They are either being deliberately inflammatory or amateurish. The management of London Underground was accused yesterday of inflaming the dispute with drivers as a further 5,000 employees were set to join the conflict. Managers told the two unions involved, RMT and Aslef, that the company would consider returning to the conciliation service Acas if the 24-hour stoppage scheduled for this Monday was called off. Union officials reacted with anger.