The Prime Minister has criticised Wales' new 20mph policy, saying it does not reflect "the right values of the British people" and forms part of "an attack on motorists".
Rishi Sunak was speaking to ITV Wales ahead of the Conservative Party's annual conference.
He said the change to 20mph in residential areas and the ULEZ policy in London are proof that the Labour Party's values and priorities do not match those of most voters.
But the Welsh Government said the change has been "thoroughly researched, debated, and voted on a number of times in the Senedd since it was put forward by a number of Assembly members in 2018, including Conservative members".
Conservatives in both the Senedd and the UK Parliament have been vocal in their criticism.
Earlier this week Senedd members pushed for and lost a vote of confidence in the minister steering the policy, Lee Waters.
Last week in Westminster, House of Commons leader Penny Mordaunt said: "This is absolutely insane even by the standards of Labour's Welsh Government".
When asked if he agreed with Penny Mordaunt, Mr Sunak said: "I think imposing a blanket 20 mile-an-hour speed limit on areas is absolutely not right. It doesn't reflect people's priorities.
"People are dependent on their cars for their day-to-day journeys and these kind of blanket bans aren't the right proportionate approach.
"But also it comes on top of this other policy not to build any new roads as well.
"You take these things together, it seems like an attack on motorists and that's rightly received the opposition that it deserves."
Only residential roads are affected, with local councils given the power to choose to keep some roads at 30mph.
Mr Sunak's response to this was to say that "you've seen the opposition from people in Wales to this policy.
"Look, it's not alone - a Labour mayor in London imposing the ULEZ charge, £12.50 on ordinary families when they're just trying to get their kids to school, take them to football practice, go weekly shopping or, you know, get to work.
"Those aren't the right values of the British people who do rely on their cars to get around and we should be supportive of them."
In response to the Prime Minister's comments, a Welsh Government spokesperson said that "the introduction of a default 20mph speed limit is designed to save lives and make our communities safer for everyone, including motorists.
"This has been thoroughly researched, debated, and voted on a number of times in the Senedd since it was put forward by a number of Assembly members in 2018, including Conservative members.
"There has been extensive consultation and it has been trialled in communities across Wales."
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