It follows the discovery that proteins in the nectar pass straight into the honey without being digested by the bee.

Researchers at the Centre for Plant Breeding and Reproduction Research in Wageningen made the find after anti-fungal proteins from common heather showed up in commercial brands of honey.

When the scientists tried feeding bees a sugar solution laced with a protein called bovine serum albumin the protein not only appeared in the honey unaltered, it was twice as concentrated.

GM plants cure dogs

By manipulating a plant's DNA, the scientists have been able to add genes for various drugs, in such a way that the drugs are secreted in the plant's nectar.

They are currently genetically engineering petunias so they yield a vaccine against a dog disease caused parvovirus.

It is hoped that bees will produce a vaccine-rich honey from the plants' nectar. "The dogs would either eat the honey as an oral vaccine, or the vaccine would be purified and injected," says biologist Tineke Creemers in New Scientist magazine.

Honey preserves proteins

The modified plants are being grown in sealed greenhouses to minimise the chances of the vaccine gene being spread by pollen. Bumblebees are being used for the experiments because they are easier to manage in a contained environment.