An internal Northern Ireland Office document, reported in yesterday's Independent, has been widely interpreted as indicating that a decision to let the Orange march through had, in essence, been taken as early as 20 June.
Last night, the Government announced that an inquiry would be held into the leak of the document. The accusation yesterday from nationalist sources - and from some Unionist elements - was that the Government had been less than frank in saying that no decision was taken until the evening before Sunday's march.
The most frequently quoted point in a day of allegations and angry recriminations was the document's statement that a consensus existed among Ms Mowlam, her deputy minister, the RUC's chief constable, the Army's commanding officer, and the chairman of the Parades Commission that "if there is no local accommodation a controlled parade on the Garvaghy Road is the least worst outcome".
A spokesman for the nationalist SDLP said: "Dr Mowlam's credibility problem was a mountain; now it is the Himalayas."
Party leader John Hume, who yesterday met Ms Mowlam for an hour-long meeting, the tone of which was described as brusque, has asked to see the Prime Minister. Brendan McKenna, of the Garvaghy Road residents' association, said the document showed "total duplicity and deceit".
Ms Mowlam insisted in a series of interviews yesterday that no decision had been made at an early stage, arguing that the document was inaccurate in saying she was part of such a consensus.
The document was written by the Northern Ireland Office's associate director of policing and security, and was endorsed by its director of security policy. When the section mentioning a consensus was put to her she said: "I agree that the sentence you've just read is difficult, I fully accept that, but if you read the paper in the whole you will see that we had not made up our minds."
Ms Mowlam continued: "There are parts of the document which I readily accept that look as if there had been a decision taken. There were numerous different documents from different civil servants with different options in. I haven't endorsed this statement, never endorsed the document."
Speaking of the nationalist reaction, she added: "I understand their anger, I understand their frustration, I understand their distress and this doesn't help. I don't believe I betrayed anybody, but I've got a lot of trust and confidence to rebuild." Mr Blair is expected to use Prime Minister's Question Time in the Commons today to reinforce his support for Ms Mowlam over her handling of the Drumcree march.
Downing Street officials said Mr Blair, who is due to fly back from the Nato summit in Madrid, had been kept in touch with events in Ulster, and "he wants to re-emphasise that Mo is doing an excellent job".
He discussed Northern Ireland in a 90-minute unscheduled session in Madrid with President Clinton, during which Mr Blair also expressed his gratitude for the President's support for the Government's handling of the crisis in Ulster.
Sporadic violence continued yesterday, with a train set on fire in Newry, Co Down.In Lurgan, Co Armagh, a train was seized soon after Orangemen had marched down the Garvaghy Road in nearby Portadown, ordered passengers off and set it on fire. The train was a total, pounds 6m write-off.
Detailing the extent of recent disturbances, the RUC said that in four days there had been 776 attacks on the security forces, 1,444 petrol bombings and 363 hijackings. Some 60 police officers and 49 civilians were injured, with the security forces firing 2,400 plastic bullets.
Last night, the republican INLA said that it had been involved in recent violence and threatened to escalate its campaign with attacks on loyalists if more Orange marches were allowed through nationalist areas.