The chairman of the Commons Welsh affairs select committee has criticised North Wales Police's anti-speeding campaign.
Police speed cameras campaign "has not saved lives"
Clwyd South MP Martyn Jones said evidence shows that the Arrive Alive scheme has not saved lives.
Mr Jones also expressed concern at the 6,500 motorists that he said have been wrongly prosecuted by the force.
But North Wales Police said the campaign had been "hugely successful" and fatal accidents had fallen by 63%.
Members of the committee will meet North Wales chief constable Richard Brunstrom over the next two days.
Mr Jones said he was not convinced by the force's claims that the Arrive Alive scheme had been a success.
"It seems to be an accepted situation that if people drive slower then the accidents are likely to be less and likely to be not as serious, but the figures actually do not show that," he said.
"The evidence isn't there. The figures do not show that lives have been saved."
"I'm sure that questions will be asked about the Arrive Alive campaign, particularly in light of the 6,500 incorrect prosecutions that have been made by North Wales Police."
He also questioned whether the campaign had targeted the most dangerous areas.
Police say the scheme has been "hugely successful"
"The mobile cameras are not being put in the places where the dangers are actually present."
"Boy-racers are not being affected by the cameras and not being slowed down."
Earlier this month North Wales chief constable, Richard Brunstrom admitted having an "obsession" with tackling speeding motorists, but denied that had affected the force's tackling of other crime.
"3,500 people die on our roads each year and something ought to be done about it," he said.
North Wales chief superintendent Geraint Anwyl said the Arrive Alive campaign had been "hugely successful."
"The facts are that the overall number of fatalities on Arrive Alive routes between April and September has decreased by 63%. This represents 10 fewer people killed."
"There are 35% fewer vehicles exceeding the speed limit on the routes and this has resulted in a decrease of 1200 speeding tickets per month."
"This is clear evidence that not only are lives being saved but overall traffic is slowing down."