Taoiseach Bertie Ahern said the numbers involved in the Dublin riots could not have been foreseen and he rejected Fine Gael claims that the low-key approach adopted by the Garda was "flawed".
Mr Ahern told the Dáil that "the proof that it was organised in my view is that you don't move from the Parnell monument to the far side of town in a matter of minutes unless somebody was calling the shots, and calling the orders".
Condemning those people who "engaged in an orgy of violence" the Taoiseach saluted the "bravery of the Garda Síochána who were sorely provoked on Saturday and responded professionally to outrageous attacks on them".
Gardaí engaged in a huge amount of planning, with numerous meetings, including six alone about securing the building site on O'Connell Street, he said.
There were 350 demonstrators and "the reality was that there were three superintendents, 10 inspectors, 32 sergeants and over 300 gardaí" involved. The air support unit was involved, the dog unit and 58 detectives were on the ground mixing with the crowd. That was not the normal Garda presence for a Saturday protest in Dublin, he said.
Fine Gael leader Enda Kenny said it was "clearly evident that there was a failure to assess properly, a failure to plan properly, a failure to anticipate properly and a failure to be ready for the worst".
Political responsibility for this failure rested with the Minister.
"And the frontline gardaí in their ordinary uniforms who had to face down those thugs and hoodlums were left unprotected and were in danger, clearly, of losing their lives," Mr Kenny said.
The level of premeditation "was in stark contrast to the low-key approach which the Government and senior Garda management appear to have adopted in respect of this march".
There was no specific intelligence available to the Garda "to suggest the violence on the scale they witnessed. That was a complete surprise," Mr Ahern said.
"They thought they were dealing with a crowd of 50 to 70 which turned out to be several hundred when they appeared out of pubs and back lanes".
Gardaí had extensive consultations over the last two months with the Northern-based organisations.
All the credible intelligence available to the Garda indicated that the counter-protest would be small and peaceful.