The PSNI and the Northern Assembly are investigating how for the first time the Tricolour was hoisted over Parliament Buildings at Stormont.

The green, white and orange colours together with what appeared to be the green Irish flag that preceded the official Tricolour were raised over this former bastion of unionism around lunchtime yesterday.

In a state which takes the issue of parades and flags very seriously this caused quite a stir. Winston Irvine of the Progressive Unionist Party complained to the PSNI which is now investigating the incident, as is the Northern Assembly.

So far the culprits have not been apprehended although the finger of suspicion is pointing in one direction. Repairs are currently taking place on the roof of the building with Stormont sources suggesting that someone directly or indirectly involved with that work may have been responsible.

The flags flew for about 10 minutes before they were taken down from the masts, said Stormont sources.

There was no peaceful meeting of minds between the Orange and Green on the affair. "I have been assured by the Assembly that these were rogue actions and are being fully investigated," said DUP chief whip Peter Weir.

“If it was carried out by someone working for an outside contractor then this surely would represent a breach of contract which should result in sanction,” said Mr Weir.

The Traditional Unionist Voice leader Jim Allister called for "robust" action against those responsible while the Ulster Unionist MP for Fermanagh South Tyrone Tom Elliott said the British union flag "is the only flag that should fly over Stormont in order to reflect and respect the sovereignty of the United Kingdom".

Sinn Fein MLA Gerry Kelly accused unionists of being hysterical in their response. Referring to the potential financial and political meltdown facing the Stormont institutions he said, "This for some unionist politicians is a bigger crisis than anything that has happened over the past weeks."