Privacy campaigners say police ask for permission to access private communications data once every two minutes.
Big Brother Watch says the Met came top with almost 180 thousand requests between 2012 and 2014.
In Northamptonshire, the figure was nearly 3,400.
In nearly 150 cases in the county, access was refused.
Cambridgeshire Constabulary had almost 2,400.
In more than 100 cases in the county, access was refused.