Undercover spot checks at petrol stations across Suffolk have revealed alarming safety lapses in the sale of petrol.
Inspectors from Suffolk County Council's Trading Standards department carried out the checks.
The operation was planned as gardeners began to top up lawnmowers as the summer approaches.
The inspectors carried out 20 random checks at petrol stations across the county and found only three passed the test.
The 17 which failed were found selling petrol in unsafe and illegal containers.
Station attendents failed to warn the undercover inspectors of the potential dangers, allowing them to fill up a leaking tin can.
A Suffolk County Council spokesman said the authority was shocked by the serious lapses in safety.
They have informed the head offices of all the filling stations concerned.