A former minister has admitted mistakes were made introducing Wales’ controversial default 20mph speed limit.

Lee Waters, who left his post as transport minister in March, told MSs a record-breaking petition, signed by nearly half a million people, made the Welsh Government sit up and take notice.

During a Senedd debate prompted by the petition, he said the Welsh Government had expected pushback, but the intensity of opposition was greater than anticipated.

He said: “Mistakes were made, particularly in not doing genuine consultation in communities and in the uneven, inflexible way the guidance was interpreted in some parts of Wales and I’m prepared to accept my role in all that.

“But let the two-thirds of members of this Senedd who supported a default 20mph limit remember this – people are alive today because of this law, together we have saved lives.”

The Labour MS criticised “deliberate misinformation” from opposition members “designed to sow confusion”, raising the example of the incorrect depiction of a “blanket” policy.

Jack Sargeant led the debate on the petition, which was submitted by Mark Baker and signed by 469,571 people – the most of any in the Welsh Parliament’s 25 years.

Mr Sargeant, who chairs the petitions committee, told the Senedd more than 17,000 people in his own Alyn and Deeside constituency added their names in support.

“There has been an unprecedented response to this petition,” he said. “And I congratulate the petitioner for amassing the highest number of signatures the Senedd has seen.”

Mr Sargeant welcomed a change in direction from the Welsh Government which will see some roads revert to 30mph – with 20mph targeted at schools, hospitals and nurseries.

Natasha Asghar said the sheer number of people who signed the petition in such a short space of time shows the strength of feeling among the public.

The Conservatives’ shadow transport secretary criticised the “draconian, divisive” policy, calling for it to be scrapped and claiming it will deal a £9bn blow to the Welsh economy.

Delyth Jewell, Plaid Cymru’s shadow transport secretary, agreed that many roads were wrongly designated as 20mph, eroding public support for the policy.