Vegetable and fruit growers are backing a call for an investigation of supermarket prices, although the retail marketers deny they are ripping off consumers with huge mark-ups.

The Green Party wants an inquiry and says growers face ruin because two giant supermarket chains are using their powerful position to force them to sell vegetables and fruit for less than it costs to produce.

MP Sue Kedgley said yesterday a survey of 75 growers found supermarkets were marking up produce by up to 500 percent.

The Food and Grocery Council has welcomed the release of a discussion document on plans to review and rationalise consumer law.

Consumer Affairs Minister Heather Roy said yesterday the discussion document focused on a "one law one door" policy.

"One law refers to the goal of principles-based consumer-supplier legislation, while one door aims to provide a single portal consumers can use to seek advice and assistance when consumer transactions go awry," Mrs Roy said.

The Food and Grocery Council seems to be acutely aware of the age-old saying, “No good deed involving confectionary ever goes unpunished by anti-obesity zealots.”

The lobby group, which represents New Zealand’s chocolate and confectionary companies, has sent hampers of various products from the likes of Cadbury, Nestlé and Whittaker’s to MPs, media and other selected people with a “”Happy Easter” message.