The head of Revenue has said a 10-year limit on pursuing tax evaders with offshore accounts was a "very strong impediment" in prosecuting Ansbacher-related cases.

State agencies and authorities have defended how they investigated whistleblower claims of tax evasion amid calls for a fresh inquiry into how they handled allegations against former politicians.

The Revenue Commissioners say that a number of Ansbacher investigations remain open, but that it is satisfied it has fully investigated claims made about former politicians by a whistleblower.

Former tánaiste Mary Harney last night denied she halted a probe into offshore tax accounts because prominent PD Des O’Malley’s name was on a list of people allegedly involved and that every opportunity had been afforded the investigation to finish its work.