Members of the Dáil's Public Accounts Committee "rolled around laughing" on Thursday when Laois-Offaly TD Seán Fleming asked Garda Commissioner Noel Conroy if it was true that the water used in cannons had been warmed up.

Conroy confirmed to the committee that the water in the cannons, which have been borrowed from the PSNI several times, is specially heated so as not to send rioters into shock.

"I know that people have the right to peaceful protest but it is a sign of the times that the water is heated for rioters in the interests of human rights, " Fleming said.

Two water cannons were borrowed from the PSNI in April 2004 before the riots and used when a riot broke out at Ashtown on the Navan Road during the summit of European Union leaders during Ireland's presidency of the EU.