Prime Minister Jacinda Ardern has promised to step in to stop RNZ's Concert FM being downgraded, saying Cabinet will look at ways to stop the much-loved station moving off the FM frequency.

And she says RNZ is obligated to keep the station running until June thanks to its NZ On Air funding - which will give the Government more time to find a solution.

Plans are afoot to move Concert to an AM frequency, laying off staff and automating playlists. The move would take place on May 29, making way for a new youth-oriented station on the FM frequency.

But following public outrage - including from former PM Helen Clark who decried the "dumbing down" of New Zealand's cultural life - the Government is now promising to step in.

Speaking at a press conference this afternoon, Ardern said she had made it very clear she was determined not to lose RNZ Concert on its FM frequency.

"Cabinet today decided to look at what would be involved in ensuring that is the case.

"From here, our expectation is that a Cabinet paper will be prepared which lays out what would be involved in freeing up the 102FM frequency.

"That spectrum has been shelved for the last 20 years for the purpose of providing youth targeted programming - something that many in this arena will be familiar with since 1999.

"In the meantime we believe Radio New Zealand has NZ On Air funding obligations to continue programming until June, and we intend to use the time available to work constructively to find a solution."

Speaking to Newstalk ZB's Mike Hosking this morning, Ardern hinted at tensions between the Government and RNZ's management over the Concert FM issue.

Broadcasting minister Kris Faafoi had expressed concerns over the proposal and had asked for time to see if something could be done to prevent the loss of the FM frequency for Concert, but "RNZ went ahead and announced this regardless", Ardern said.

"We tried to and asked for some time to explore and investigate how we could make sure that this wasn't an outcome that RNZ subsequently announced anyway.

"I'm pretty frustrated by that situation. It's unacceptable."