MR JOHN MAJOR has warned: "No one will take Sinn Fein seriously ever again until they show a serious commitment to end violence for good."

And the British Prime Minister has expressed his most personal commitment to the Union, telling the Conservative Party conference: "I don't believe Northern Ireland will leave the United Kingdom, nor do I wish it to."

While British ministers maintained no doors had been closed, Mr Major said Sinn Fein had slammed the door on themselves by their own action".

The Government was last night considering the implications of Mr Major's announcement that he proposes "to make government in Northern Ireland more accountable" by beefing up the Northern Grand Committee at Westminster, on the Scottish and Welsh model.

Dublin was not informed in advance about the announcement, which will inevitably be seen as a concession to the unionists, and which they will regard as an integrationist" measure.

In a blistering attack on the republicans during the most substantial and heavily applauded section of his speech the Prime Minister said of Monday's bombing in Lisburn: "Earlier this week the IRA once again spat their hate at the British nation."

And, as he announced the death yesterday of Warrant Officer James Bradwell, Mr Major made a powerful personal attack on the Sinn Fein president, Mr Gerry Adams: "Warrant Officer Bradwell was aged 43, with a wife and children, Mr Adams... I sent him there, Mr Adams, so spare me any crocodile tears." And to powerful applause, Mr Major continued: "Don't tell me this has nothing to do with you. I don't believe you, Mr Adams."

Mr Major said "the IRA's latest betrayal of Northern Ireland" meant "the demand for decommissioning of illegal arms" was ever more clearly justified. And he announced his government would publish its proposed legislation in the autumn to provide for a decommissioning process.

"So that there's no hiding place for those arms, missiles and explosives, Paddy Mayhew will introduce legislation into parliament . . . to set out how they can be taken out of circulation," Mr Major said.

He went on: "I want those weapons off the streets. And I want to remove the false excuses peddled by the men of violence for keeping their weapons. Let us expose these men to the world for what they really are.

I applaud the way the loyalists have maintained their ceasefire in the face of the IRA's provocation. Their political leaders have gained in influence and standing as a result. I urge them to stand firm and not to throw away what they have achieved."

Announcing his move on the grand committee, Mr Major told the conference: "We have already given the Scottish and Welsh MPs greater ability to question ministers. This autumn I shall do the same for Northern Ireland.

MPs from there should be able to question ministers and scrutinise government policies directly in the grand committee meeting sometimes in Northern Ireland. I will consult the parties about how best to achieve that."

Pledging his continuing commitment, Mr Major said: "Many good people tell me that I shouldn't bother with Northern Ireland. `No votes in it' they say. Maybe not. But there are lives in it. That's why I bother with Northern Ireland."

And he went on: "But I know there can only be a peace in Northern Ireland if all its citizens - Catholic and Protestant alike - feel their traditions have a welcome place in our United Kingdom. And there will only be peace of mind if we remove the causes that have given rise to so much conflict over so many years.

Progress in the multi party talks had been painfully slow he said, "but progress has been made. And there is no other show in town. Bombs will never bring Sinn Fein into the talks. All they mean is that Sinn Fein have slammed the door on themselves."

"The IRA has always believed that Britain can be deflected by terrorism. They're always been, wrong. And they re wrong now, Mr Major added.

Dr Mo Mowlam, Labour's Shadow Northern Secretary, gave a distinctly cool response to Mr Major's announcement on the grand committee.

"As far as improving accountability is concerned," she said, "the only sure way is through devolution as part of an overall balanced settlement that addresses the totality of relationships.

Prior to a negotiated settlement, if John Major wants to improve accountability and openness in Northern Ireland, it is important that it happens across the board, not just in Westminster.

For example, Labour had proposed the introduction of a Freedom of Information Act, and measures to make quangos more open and representative, Dr Mowlam said.