More than 150,000 people have signed a petition demanding that the Welsh government “rescind and remove the disastrous 20mph law” which came into effect on Sunday.
Because more than 10,000 people have signed the petition it will be sent the Welsh Senedd petitions committee for consideration.
The Welsh Conservatives are against the scheme and have said lower speeds will cost between £2.7 billion and £8.9 billion and will increase journey times.
Natasha Asghar, Welsh Conservative shadow transport minister, said: “For more than 150,000 people to sign a petition within such a short space of time highlights the extent of public outrage towards Labour’s disastrous policy.
“Labour and Plaid Cymru have refused to listen to public opinion and are continuing to wage their anti-worker, anti-road and anti-motorist agenda.”
Lee Waters, deputy minister for climate change, said: “It’s simple – slower speeds save lives and help create safer communities for those that live there.
“Evidence shows that a vehicle travelling at 30mph will still be travelling at 24mph in the time it would take a car travelling 20mph to stop.
“We know decisions like this can be unpopular and we know that change is never easy, but what’s one minute on your journey time if it saves a life and reduces a lifetime of human misery for families affected.”