Fly-tipping is ruining parts of the countryside while costing councils thousands of pounds to clean-up, according to new figures.
Statistics collected by Plymouth City Council rank the authority second in the table of shame in the South West while Cornwall Council's data comes third.
Plymouth's figure for 2010/11 was 3,792 showing 902 less than for the previous 12 months.
Similar recent figures for Cornwall reveal 3,144 cases indicating an increase of 493.
Councils across the rest of Devon reported a decrease in cases, apart from West Devon Borough Council, whose figures rose 41 to 327.
Thirty-six councils in the South West submitted data to Defra, which compiled the list.
Union leaders said more should be done to tackle the blight.
John Philips, GMB regional secretary, said "Not only is fly-tipping illegal but it is damaging to the environment.
"Two thirds of fly-tipping involves household rubbish and we believe it would make good economic sense to invest in more municipal waste and recycling centres to make it easier and cheaper for the public to dispose of waste properly.
"Some councils have redefined fly-tipping so that even five bin bags left on the street is classified as litter and not fly-tipping – this would explain why some of the figures are well down on the previous stats.
"However, local authorities also need to target fly-tipping to improve their policing of the problem.
"Secretary of State Eric Pickles should lead a campaign to clamp down on fly-tipping while allowing councils extra money to invest in better waste facilities."
Last year Plymouth Council spent £159,592 clearing up after fly-tippers – the majority of violations occurred in back lanes. A council spokesman said: "Some areas such as Mutley and Greenbank have significant problems with this at certain times of the year.
"We are in touch with landlords to make them aware of this problem, but this can be a recurring and frustrating problem."
Cornwall Council was last night not able to say how much it spent clearing-up after fly-tippers but a spokesman said: "There is no excuse for fly- tipping – the council provides a range of services that enable people to properly dispose of their waste including kerbside collections as well as Household Waste Recycling Centres where people can take their waste free of charge."