Prime Minister Tony Blair has issued a fresh call to the IRA to take a big step forward.

In an interview in Friday's Irish Times newspaper, Mr Blair refuses to use the word disbandment but makes clear paramilitaries can no longer use force in order to achieve political goals.

His comments come a day after another arrest in a police investigation into allegations of IRA spying at Stormont.

In his most significant interview since a speech in Belfast last month, Mr Blair again stresses that the process of transition from violence to democracy is over.

In his earlier keynote speech in Belfast, the prime minister said: "We cannot carry on with the IRA half in, half out of this process. Not just because it isn't right any more. It won't work anymore."

Gerry Adams: Mr Blair's previous call angered republicans

However, republicans reacted angrily to Mr Blair's call last month, saying the IRA would not respond to ultimatums.

Northern Ireland's power-sharing executive was suspended for the fourth time last month following allegations of IRA intelligence gathering in the Northern Ireland Office.

In Friday's newspaper interview, Mr Blair says there is no point in trying to inch forward or engage in choreographed steps.

The prime minister said an act of completion is what is required - in other words a big step forward that will enable the government to fully implement its part of the Good Friday Agreement.

And Mr Blair ruled out renegotiating the Agreement, insisting the parties will keep coming back to the same issues to be addressed in the same way.

Mr Blair said there can be no mixing of paramilitaries and politics.

Reacting to the article, Sinn Fein chairman Mitchel McLaughlin said Mr Blair "may be partially right but he's not wholly right" in saying that paramilitarism was the root of all of Northern Ireland's problems.

Mitchel McLaughlin: "British Government must honour its commitments"

Speaking on Radio Ulster on Friday, Mr McLaughlin added: "You can't make demands of one side whilst admitting at the same time that you have not fulfilled your own."

Last week, the IRA announced it was breaking contact with the international decommissioning body following the suspension of the power-sharing institutions.

It said it had taken the decision to stop engaging with General John de Chastelain's organisation because the British Government had "by its own admission" not kept its commitments under the Good Friday Agreement.

However, in a statement the IRA said it remained "committed to the search for a just and lasting peace".

In a tough message to loyalists Mr Blair warned that paramilitary acts must cease completely and signalled the time has come to treat paramilitaries as criminals.

He told the Irish Times he was "physically sick" when he heard loyalists had crucified a young man at the weekend.

He added these people must realise that the government intends to come down on them with every bit of force and authority it can.

Meetings continue

Unionist politicians have led calls for the IRA to disband amid further crisis in the political process.

They also demanded Sinn Fein's expulsion from government over allegations of IRA activity, including claims it was involved in training left-wing Colombian guerrillas and was behind a break-in at the police's Belfast headquarters in March.

Meanwhile, the Irish Republic's Foreign Affairs Minister Brian Cowen continued meeting with delegations from the parties in Belfast.

He met Sinn Fein's Martin McGuinness and the leaders of the Progressive Unionist Party and the Alliance Party on Friday.

Speaking after the meetings, Mr Cowen said any multi-party talks aimed at ending the political crisis would have to address concerns on all sides.

And he said there was still a lot of work to be done.

"There are issues out there including the full implementation of the Agreement which have to be agreed on by all of the parties," he said.