The WWF Paper Scorecard aims to give paper buyers an objective means of comparing the environmental and social impact of different papers.

However on the issue of sourcing the WWF will only rate FSC-accredited stocks.

The PEFC has said that by only recognising what amounts to 3% of forests and a third of certified forests, it is lumping other accredited stocks together with uncertified products.

It suggested the WWF is partisan given that it was one of the original supporters of the scheme and claimed ignoring others "calls the entire scorecard into question".

A spokesperson told printweek.com that in a study of the various accreditation systems, PEFC stocks demonstrated "inconsistency across measures" that made it more difficult to assess. They described PEFC system as "not as transparent" and "in most cases actually inferior".

The PEFC has urged the WWF to open the door to it and others to change the scorecard system so that its requirements can be met by other "credible certifications" and address concerns.

The WWF was unmoved by the motion, describing FSC as "the only one that meets the environmental and social standards that we think are necessary to certify a forest.