Senior Gardaí are taking industrial action in a new pay row.
The Association of Garda Superintendents says from today they will not take on any extra duties.
They are unhappy about what they call a 'pay anomaly', that sees superintendents lose out on up to €6,000 after promotion from the rank of inspector.
The issue was supposed to have been dealt with during a side-deal avoiding a strike two years ago.
But the Association's General Secretary, Denis Ferry, says that agreement has not held.
He said: "That has left us in a situation where there is now a significant pay anomaly.
"We now have people being promoted and they are probably paid between €4,000-€6,000 less that the inspector and that is unprecedented."