However they are still generally quite happy with their brands, as the overall rating of 65.9 out of 100, compared to 66.7 last year, is a positive result.
Of the 34 brands in this year's survey, 15 achieved improved average dealer ratings while 19 saw their ratings decline.
Lexus, highest rated since 2006, dropped to third place following a 10.2 decline to 77.4 points, to be replaced at the top by Mini, with a 0.8 improvement to 78.1 points.
At the bottom languishes Subaru, also bottom last year, with a 4.7 point decline to 45.1 points.
Highest mover is Kia, with a 15 place rise to 15th due to its 8.8 point improvement to 67.3 points.
Kia Motors (UK) managing director Paul Philpott said this reflected the brand's focus on developing support for the network and building the strength of the brand.
He added: "It is a strong endorsement of the hard work the entire company has put into ensuring the profitability and professionalism of the franchise over the last 18 months that we are now seen as one of the more attractive franchises and that dealers believe we have improved our levels of service to them in every area."
Biggest faller is Proton, which slumped 19 places to 32nd with a 16.2 point decline.
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