"We have shown that there are not only environmental benefits that can be gained, but also yield increase can be made in the production of pulp," said Dr Claire Halpin, senior lecturer at the University of Dundees school of life sciences.

In 1995 a team of French scientists from the Institut National de la Recherche Agronomique produced genetically modified poplars and used them in field trials in France.

At the same time Dr Halpin started another field trial in Berkshire.

The poplar trees were modified to alter the structure of their lignin content, making it easier to extract and reducing the amount of chemicals such as alkali being used.

The lignin must be extracted from the wood to make paper, a process that normally involves a lot of energy and chemical usage.

Halpin said the yield increases for pulp per unit of wood were as much as 3%, indicating lower tree-use in the pulp production process.

During the five years of research the modified trees showed no adverse signs of effects on their growth, disease resistance, or on the numbers and varieties of insects living in the trees.

The research was funded by the EU Commission.