The Minister for Public Expenditure and Reform Brendan Howlin says any breach of official pay policy by voluntary hospitals or health agencies have to be addressed.
It has emerged that a number of voluntary hospitals are giving some of their senior executives top-up payments from private sources, such as shops on hospital campuses.
The Master of the National Maternity Hospital in Dublin, Dr Rhona Mahony, received a top up of €45,000 in addition to her salary and allowances of €236,000 and it is unclear where the payment came from.
Minister Brendan Howlin says there should be no top-ups.
He said: "Firstly I think there should be transparency on the pay levels of anybody on the public pay roll.
"There's clearly an opaqueness about some in the health sector and that should be clarified, we should know what people are paid.
"There should not be top-ups per se, there should be transparency in relation to a clear rate of pay for the job."