Fraudsters use information freely available on council websites to con councils out of cash.

Criminals have got away with £7m at least by posing as contractors.

The cheats ask council finance departments to redirect payments for work to bogus bank accounts they have set-up then pocket the cash.

Councils claim they have now wised-up to the con and have already prevented losses of another £20m this year.

The commission said: “Criminals use data to mislead and to redirect payments to and from public bodies.

“The fraudsters have sent letters to council finance teams that appear legitimate and often follow them up with phone calls to chase payments.”