A well-known Wellington supermarket is joining the call to charge extra for plastic bags - if not ban them altogether.

Wellington mayor Justin Lester uniting with other mayors around the country to put pressure on the government to impose a levy or give councils the power to do so.

Moore Wilson's has been a retailer in the capital for almost a hundred years and now has stores in Wellington, Lower Hutt, Porirua and Masterton, which is why sales manager Amanda Thompson points out that the decision would have to be made by central government rather than local councils.

"It's a good reminder for people that there are alternatives there and that no one is being forced to take a plastic bag. We try and make it as easy as possible for them not to use them."

Greg Harford, Retail NZ public affairs manager, agrees that the decision would have to come from government because of Commerce Commission rules about price fixing.

"It's actually illegal for retailers to agree amongst themselves to levy a fixed price for a plastic bag or indeed any other product," he relates.

Further, Harford says local alcohol policies and Easter Sunday trading hours are proof the legislation needs to be government-led.

"It becomes very complex and costly for everyone, community groups, retailers, and indeed local councils, to administer."