A senior Ulster Unionist has called for a public inquiry into allegations of IRA intelligence gathering at Stormont.

The call came from Michael McGimpsey, the former culture minister in the Northern Ireland Assembly before its suspension in October, during the row over the allegations.

He said: "I believe this spy ring penetrated to the very heart of the security situation in the Northern Ireland Office.

"There has to be a public inquiry into all of this because all of us are feeling disquiet."

Michael McGimpsey: "We are trying to create a new society"

Mr McGimpsey made the comments after Acting Deputy Chief Constable Alan McQuillan said on Monday that the police had broken up a major IRA intelligence gathering operation in Belfast during their investigation.

Four people, including Denis Donaldson, head of Sinn Fein's administration at the Northern Ireland Assembly, were charged last month after police seized documents in raids on republican homes.

A civil servant who had access to the offices of the first and deputy first minister was arrested last week, but was released without charge. He has been suspended on full pay.

'Time for change'

Sinn Fein has pointed out that there have been numerous leaks at the heart of government over the years in Northern Ireland.

Mr McGimpsey did not deny this, but he said his party was focussing so closely on the latest allegations because it was now time for Northern Ireland to change.

He said: "What we are about, after 30 years of violence, is creating a new society in Northern Ireland and making sure the next generation doesn't go through what we went through.

Sinn Fein's Mitchel McLaughlin: "Allegations unproven"

"And that is why the actions of parties in Northern Ireland are so important, whether you regard them as responsible or not."

He added: "At the moment, and for some time, the major obstacle to making the process work has been republican inability to live up to their obligations under the Agreement."

However, Sinn Fein chairman Mitchel McLaughlin said while people were facing charges, none of the allegations had been proven.

He said the important point was that Sinn Fein's project was a political one and while the row over the allegations continued "politics is in paralysis and that it not good for anyone".

'Not offensive'

On Monday, the acting deputy chief constable said the breakthrough followed the investigation into the break-in at Belfast's police headquarters in Castlereagh in March.

Mr McQuillan said the investigation had taken the police "into the very heart of the Provisional IRA".

Thousands of documents and hundreds of computer disks are being examined by 40 detectives who are working on the Castlereagh case and the alleged IRA intelligence gathering operation at Stormont.

Mr McQuillan alleged some of them had been copied in the Northern Ireland Office, while some had been "originated within the IRA".

But he said he had nothing to suggest the IRA had any intention to use the information from Stormont in any offensive way.

He added that he wanted to address the concerns of Catholic civil servants.

"We are very conscious that some people working within government who are decent, honest, people may well have been approached and may well have had pressure put on them to provide information," he said.