The deputy leader of the Ulster Unionist Party, Mr John Taylor, said the British government's review of the Provisional IRA ceasefire was in "total disarray".
He was speaking after the Northern Secretary, Dr Mo Mowlam, publicly contradicted the Minister for Foreign Affairs, Mr Andrews, when he said both governments considered the Provisional IRA ceasefire to be intact.
Mr Taylor said the apparent disagreement had "let the cat out of the bag" over the ceasefire review's final outcome. Dr Mowlam had left Mr Andrews "isolated" and it was "quite amazing" the British and Irish governments were not on the same wavelength.
"Clearly they were in total disarray with Mo Mowlam disagreeing with what the Southern Irish Minister, David Andrews, said," Mr Taylor added. "But I do believe he let the cat out of the bag. There is already an understanding between them that the IRA ceasefire has been held. We would disagree with that in Northern Ireland."
The Northern Secretary is to announce her decision on the state of the Provisional IRA ceasefire later this week. She will be deciding if the murder of Mr Charles Bennett and the transatlantic gun-smuggling attempt were breaches of the ceasefire.
Both Dr Mowlam and Mr Andrews insisted there was no disagreement between the two governments on the ceasefire issue.
Mr Taylor said the UUP's next move would depend on the outcome of Dr Mowlam's considerations. "But as far as we are concerned the IRA have been active since the signing of the Good Friday agreement - not only being involved in killing some people but, of course, breaking the limbs of nearly 500 people in punishment beatings and, worse still, in exiling 500 Catholics," he added.
Mr Taylor said that after the "faux pas" with Mr Andrews, it was clear Dr Mowlam was not in charge of the situation. "I'm not sure that anyone is at the moment. The thing is unscrambling," he added.
A DUP Assembly member, Mr Sammy Wilson, accused the UUP of hypocrisy. Only last week the party's security spokesman, Mr Ken Maginnis, had urged Dr Mowlam not to expel Sinn Fein from the review of the Belfast Agreement yet now the party was "pouring criticism on the Irish and British governments for their differences of opinion on the IRA adherence to a ceasefire", he said.
The Alliance chief whip, Mr David Ford, urged Dr Mowlam to provide a "clear, tight and unambiguous definition of what is meant by a ceasefire when she makes her statement on the status of the IRA ceasefire later this week".
Meanwhile, Mr Taylor has predicted that the Patten Commission on the future of the RUC will recommend dropping the force's name.
He said this would be overwhelmingly rejected by people in Britain and the North. "It is a highly emotional issue and there will be a very strong campaign throughout the UK to support the RUC and retain its name," he said.
Mr Ian Paisley jnr of the DUP said the UUP had no right to complain about the Patten Commission. "John Taylor's outburst against the commission fools nobody. He initiated these changes by accepting the Belfast Agreement. The UUP signed the death warrant of the RUC, but today they are having second thoughts and attempting to be their saviour."
A UUP MP, the Rev Martin Smyth, said the Patten Commission should support the RUC, not recommend "cosmetic measures to appease terrorist gangsters". A name change would not win the force support among republicans anyway.
"The Royal Irish Constabulary was 80 per cent Roman Catholic yet its personnel were treated by republican Sinn Fein/IRA in the same way as they continue to murder and attack the RUC."
But an SDLP Assembly member, Mr Alex Attwood, said changes in policing were inevitable, although he refused to speculate on exactly what they might be.
"I've no doubt there will be significant structural changes. But people need to recognise that if we're going to have a representative, accountable police service, then there are going to have to be changes."