Police documents obtained by Radio New Zealand show the Treasury is against buying more speed cameras with money earmarked for road policing.
It says new cameras should be funded through the main police budget, not through the road policing budget.
But the police, who receive about $300 million a year from the Transport Agency's National Land Transport Fund for road policing, say they disagree.
They say the Treasury's position is not viable, as it's unlikely new capital projects would be approved that way.
The documents say buying about 25 speed cameras for nearly $4 million is of great importance to the police, as the equipment is aligned to the national road safety strategy.
While it had been intended to install some new cameras by July, the police say these cameras have not been purchased, and further work is being undertaken.