A number of construction sites in Dublin face further industrial disruption tomorrow as Unite steps up its dispute over pay rises for crane operators.

The operators will be picketing three sites in Dublin: two John Paul sites on Sir John Rogerson's Quay and Windmill Lane, and the Bennett's site on City Quay.

Unite Regional Organiser Tom Fitzgerald said five other sites would be affected as crane operators from there will be joining the pickets at John Paul and Bennetts.

Last week's industrial action, which closed two sites on Thursday, only involved staff hired through employment agencies and non-Construction Industry Federation firms.

However, tomorrow Unite will reveal the result of its ballot of all members working on CIF sites, raising the prospect of nationwide disruption across the construction sector.

The CIF has already described the Unite pay claim as unsustainable and the strike action as irresponsible.

Meanwhile, the dispute between SIPTU and Unite over who has the right to represent the crane drivers remains unresolved.

The outcome of an Irish Congress of Trade Unions disputes committee hearing into the row is awaited.