Public Expenditure Minister Brendan Howlin said that there needs to be greater transparency in the area of pay for public servants.

His comments come after it was confirmed the Coalition could not stop salary "top ups" from people who have them since before 2010.

The controversial bonuses emerged two years ago in voluntary hospitals and other health service managers, including at the Central Remedial Clinic.

Brendan Howlin said that legally in many cases the coalition cannot take away the payments.

"Certainly in the public service, we need to have complete transparency in how pay is made up," he said.

"We need to ensure that headline figures are actually in compliance with pay norms and that we have control over the public pay bill, and that's something that we have fundamentally altered in the last few years."