A change to speed limits could be introduced nationwide as the National Police Chiefs Council say they indented to review the guidance.
It comes after fines for speeding in London have soared in recent years after the Metropolitan Police lowered the ‘enforcement threshold' without an official announcement.
The rules previously stated drivers would not face legal action for going too fast unless they were over the 10% and three mph.
This means that motorists would be able to drive at 25mph in a 20mph zone before they could be charged.
Resulting in around 347,000 motorists prosecuted for speeding between January and June this year, compared to the 97,000 in the six months before the force changed the rules.
But the Met says the 259% increase comes because of ‘capacity and is not related to the enforcement threshold change’.
In response to the increase, the Met said: “Posted speed limits are the maximum speed that road users should travel at any time ... irrespective of the speed threshold that police commence enforcement action."
Although the rule change is currently just affecting those based in London, with the National Police Chiefs Council reviewing guidance there is a potential for the 1mph to impact drivers across the nation.