The controversial 20mph speed limit introduced last year on hundreds of roads in Wales could be be returned to 30mph - although the Welsh government said the limit will remain in built-up areas and around schools and hospitals.

The Welsh government denied the move is a U-turn, describing it as a fine tuning of the policy. Ministers are now urging the public to have their say on which roads should be returned to the 30mph limit, before the changes kick in at the end of the year.

The Welsh transport secretary, Ken Skates, said: “It’s not a U-turn. This is about refining and finessing a policy that will help make Wales safer. I think it’s important to be able to listen to people and show humility and accept where errors have been made.

“I don’t think it’s embarrassing for us to have pursued a policy that will make Wales feel safer, reduce collisions, hopefully save lives and save the NHS valuable time and financial resource. I don’t have a problem at all in saying to people, I’m sorry if we’ve got elements wrong, we will correct them.”

He said the changes to the 20mph limit could affect hundreds of road, adding: ”It will vary quite significantly across Wales. For example, in Cardiff there may only be half a dozen changes because it lends itself so well to 20mph, whereas in other parts of Wales that are more rural and semi-urban, we may see far more changes.

“Overwhelmingly, though, what I hear is that outside schools, outside hospitals, in built-up areas, outside of playgrounds and so forth, 20mph is the right speed. But there are some routes where 30 is more appropriate.”

The revised guidance on 20mph roads will be published in July, with councils expected to start detailed consultation on changes from September. The cost of the changes could amount to £5m, Skates said. The cost will be covered by the Welsh government and not by councils.

Natasha Asghar, the Tory shadow transport minister in the Senedd, described the policy as shambolic and called for it to be scrapped ”in its entirety, so commonsense can prevail and 20mph remains where it is needed such as outside schools, play areas, high streets, places of worship, etc.”

The campaign, entitled 20’s Plenty, said: “It is entirely correct to review the guidance and the way that it has been interpreted and used by highway and local authorities.

”This should be done with the aim of making it clearer rather than having any pre-conceived idea of diluting the guidance to allow greater freedom to set higher limits.”