The PPA and Royal Mail are set to meet and reach a compromise over the proposal that items 10mm-thick could be classified as packages rather than large letters, depending on a tolerance level of 2mm.

The PPA argued that the uniformity measure would cause a "substantial increase in costs".

But Royal Mail has agreed to scrap plans over a flexibility measure. The proposals were based on how rigid or flexible items were. Cost increases could have been imposed if Royal Mail had found the items caused delivery process.

"We very much welcome the decision by Royal Mail not to pursue the concept of flexibility," said VNU Business Publications managing director Brin Bucknor. "But we still have a number of serious concerns over the issue of uniformity."

The Royal Mail offered a robust defence of its plans and said that the proposals were "totally objective and clearly defined" for all mail weighing under 1kg.