Thieves stole metal more than 100 times in Dyfed and Powys last year and over 30 times in north Wales, figures show.
The AA said metal theft – which includes the theft of valuable car parts – rises when household budgets are squeezed.
Office for National Statistics data shows Dyfed-Powys Police recorded 107 metal theft offences in 2021-22 – though this was down from 145 the year before.
Of the thefts last year, 27 were infrastructure-related, which includes the stripping of metal such as roofing lead from buildings, taking electricity or railway cables, or stealing vehicle parts.
The remaining 80 were non-infrastructure related, which could involve stealing scrap metal or war memorial plaques.
This is equivalent to a rate of 2.1 offences per 10,000 people in the area – down from 2.8 per 10,000 people the year before.
In North Wales Police 31 metal theft offences were recorded in 2021-22 – just one less than the 32 the year before - all of which were infrastructure-related.
This is equivalent to a rate of 0.5 offences per 10,000 people in the area – unchanged from the year before.
Across England and Wales, 30,100 metal theft offences were recorded last year – up from 19,000 a year earlier, and the highest number since 2013-14.
Almost two-thirds of these were related to infrastructure – the highest proportion since comparable records began in 2012-13.
Rates of metal theft fell from 2012-13 – around the time the Scrap Metal Dealers Act, brought in to crack down on the trade in stolen metal, was introduced.
However, the Local Government Association said rates have since risen due to several factors, including a significant increase in metal prices.
Nesil Caliskan, chair of the LGA’s safer and stronger communities board, said: “Metal theft is extremely damaging and costly and has the potential to affect a range of people and businesses.
“Councils work hard to support businesses to meet the requirements of the relevant legislation, targeting their resources as efficiently as possible, and can take enforcement action where issues are identified.”
The LGA is calling for the Government to introduce an offence within the Scrap Metal Dealers Act for receiving cash for scrap metal, as well as specific funding to support enforcement to help local authorities.
Jack Cousens, head of roads policy for the AA, said: “When there is a squeeze on household budgets, sadly crimes such as metal and car part theft rise.
“The two main reasons are the steady price in scrap metal values and thieves selling parts on the black market.
“While reputable scrap merchants uphold and implement the rules when it comes to selling metal, more needs to be done to tackle the yards willing to turn a blind eye when a big delivery comes in.”
The AA called on the Government to recruit and train more police officers to deter thieves from stealing parts in the first place.
A Home Office spokesman said: “We recognise the impact that theft can have on victims and we want offenders charged and brought to justice in the courts.
“We are giving police the resources they need to keep us safe, including by recruiting 20,000 extra police officers and providing funding to the National Infrastructure Crime Reduction Partnership which ensures the police and law enforcement partners work together to tackle metal theft.”