In a widening of its claim last month that the proposals could "wipe out" A3 weekly news-based tabloids, the PPA said that A4 titles "straying marginally" over the 10mm thickness and 250g weight thresholds could be hit by mailing cost increases of over 250%.

The findings had "major implications" for marketing and advertising activity, especially cover mounts, it added.

The Royal Mail is analysing consultation feedback following the 30 June deadline, and plans to put its case forward to the postal regulator in September.

The PPA said its latest findings were "yet another example clearly demonstrating that size-based pricing does not suit the dynamics of the magazine industry".

If approved, the structure would come into force from October 2003.

Story by Gordon Carson