Norfolk's police and crime commissioner has sparked anger after saying many of the county's 20mph speed limits will never lead to speeding drivers being taken to court.
Giles Orpen-Smellie said many 20mph signs are merely advisory, meaning motorists who drive between 20mph and 30mph cannot be prosecuted.
He has called for a change in the law so that Norfolk police could take speeders to court.
However, campaigners have hit out at the Conservative commissioner's remarks, claiming Norfolk Constabulary already can and should be taking enforcement action.
Experts and organisations have issued contradictory views on the issue, deepening confusion over it.
The number of 20mph limits and 20mph zones in Norfolk has increased greatly in recent years, with Swaffham due to become Norfolk’s first 20mph town.
However, the most recent published data shows that there have been no prosecutions in Norfolk of motorists speeding in 20mph areas.
The issue arose at a recent Norfolk County Council meeting, where a member of the public asked why that was the case. 
Mr Orpen-Smellie, who was attending the meeting, said: "It's more complicated than it seems. The minimum speed limit in law is 30mph.
"I appreciate there are lots of 20mph signs displayed. They are usually advisory, unless they are backed by specific law.
"It's therefore extremely difficult for the police to prosecute because, despite the 20mph sign, despite it being written inside a red circle - which normally indicates it has legal force - if it goes in front of magistrates they will throw it out, because there is no basis in law to prosecute.
"I am hoping for a change in the law because I get asked the question almost weekly: 'There are 20mph signs about, why doesn't the constabulary enforce them?'
"They would love to."
However, Mr Orpen-Smellie's remarks prompted anger from Liam Calvert, of the Norwich branch of charity Living Streets, who asked the question following the death of two cyclists on Norfolk roads within the space of 48 hours.
He said he was "amazed" at the remarks and said: "Given the regular enforcement that takes place in other parts of the country, I will be very keen to hear more about the advice he has received from officers on the issue.
"20mph limits are there to improve safety and, just as importantly, increase the feeling of safety for vulnerable road users."
Rod King, director of campaign group 20's Plenty For Us, branded Mr Orpen-Smellie's comments as "absolute nonsense".
He said: "20mph limits are as enforceable as any other limit. In 2021, Avon and Somerset Police issued 23,338 notices of intended prosecution on roads with a 20mph limit."
A spokesman for the National Police Chiefs' Council said: "Enforcement is a matter for individual forces based on their consideration of risk and harm, but all speed limits are technically enforceable, including 20mph limits."
READ MORE: Opinion: The big policing problem with 20mph speed limits
A spokeswoman for Norfolk Constabulary said there was a difference between 20mph limits and 20mph zones.
She said: "A zone can be introduced by a local authority without any permissions being sought. However, this can create a significant issue for enforcement.
"If a zone is introduced without a traffic order then the speed limit applicable will be 30mph, as it will fall within the remit of a restricted road, despite the advisory 20mph signs."
She said Department for Transport guidance was that 20mph zones and 20mph speed limits should be "generally self-enforcing", given road conditions and measures such as signs and traffic calming.
The spokeswoman said: "Police enforcement in 20mph limits and zones will not routinely take place but may be appropriate if there is clear evidence of significant non-compliance or injury collision history supports such action.
"Where drivers are regularly and wilfully breaking the law, officers will enforce the limit and seek to prosecute offenders."
But she said the force did not issue tickets for speeding in 20mph areas.
Norfolk County Council said it followed central government guidelines when determining and introducing speed limits.
A spokesman said: "This includes following a legal process and a public consultation for any legal changes to speed limits.
"In some cases, advisory part-time 20mph speed limits are displayed, typically outside schools, to highlight additional dangers to drivers."
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here