Leo Varadkar believes the gardai could be called in to investigate RTE’s secret slush fund because some of the payments may have been illegal.
The Taoiseach’s comments came after Garda Commissioner, Drew Harris, said that the force is ready and able to conduct a probe if asked.
Mr Varadkar was in Brussels for the European Council summit of EU leaders on Friday.
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He told reporters: "I don't think we can rule out the fact that it's not just a case of irregular payments, that some of these payments may have been on the wrong side of the law. But I don't want to jump to that conclusion.”
"The fact that it was so untransparent, even concealed, that payments were made for work that perhaps wasn't done. That's much more serious, I think, and is a matter of real concern."
He added that he was "not sure" if the gardai need to be called in yet: "It did concern me to hear that payments were - or it would appear anyway - that payments were made by RTÉ to outside contractors for work that wasn't actually done.
"RTÉ receives public money from the licence fee and other sources and receives commercial money from advertising and commercial partners and that all goes into the one pot.
"I'm not sure that's going to be appropriate going forward. I know, as someone who's a trustee of a political party, we have to keep the public money separate from the money we raise ourselves, we have to produce separate accounts.
“And I'm wondering, might it have been better if [RTÉ] operated on that basis."
The Taoiseach warned RTE about holding back documents from the PAC on ‘legal privilege’ grounds. He said: "That does depend on circumstances.
“Legal privilege is there for a reason and does need to be protected. I don't know the exact circumstances that are there, but individuals, companies, governments use legal privilege because if you're involved in a court case if somebody's suing you, and the fact that you're forced to release all your documents and the other side isn’t, puts you at an enormous disadvantage.
"So there is a reason for legal privilege. I don't know whether it's appropriate in this case or not. I just don't know enough about it."
Meanwhile, Garda Commissioner Drew Harris has said the force is not investigating the RTE payments scandal – but will if bosses in the national broadcaster ask it to.
