THE consumer watchdog is warning retailers who display an anti-carbon tax poster being distributed by Tony Abbott's office that they could inadvertently find themselves misleading customers, a breach that carries fines of up to $6600.

Mr Abbott and the Coalition's small business spokesman, Bruce Billson, have sent out an estimated 7000 posters to bakers, bottle shops, butchers, cafes, dry cleaners and fruit shops. The campaign, which includes an accompanying letter, is targeting small, marginal Labor seats.

The posters include the statement: ''We always strive to keep our prices at reasonable levels but because the carbon tax will make electricity and gas more expensive, our prices will increase.

''We apologise for these price increases.''

The Australian Competition and Consumer Commission said the poster itself was not misleading. But if a shop displayed the poster, and then raised its prices for reasons other than the carbon tax, customers might believe the rises were entirely the fault of the carbon tax. The watchdog expressed concern about this, saying customers might be misled.

''The ACCC acknowledges that the flyer in itself will not raise concerns,'' it said. ''However, it is important that businesses that use the flyer do so in a manner that won't mislead consumers by confusing other price increases unrelated to the carbon price.''