The changes will come into effect on 3 April, but remain subject to alteration if Royal Mail does not accept regulator Postcomm's overall price control, after a period of consultation ending in March.

Bulk mail services Mailsort and Presstream will suffer as first and second class stamps rise by 2p.

"Now that the UK market is open to full competition, it is essential that our prices are more closely aligned to the true cost of collecting, sorting and delivering," said Royal Mail director of commercial policy and pricing Lorna Clarkson.

But DPS Direct Mail technical director David Laybourne warned that the rises could lead to Royal Mail customers looking elsewhere for mailing services, particularly if margins became tighter. "Any price increase is unwelcome especially given the softening of the market," he said. "We will be looking for service-level improvements from Royal Mail to mitigate the rises. It is clearly sheltering businesses from the increase as much as possible by creating different base prices for business as opposed to consumer mail."

Both Presstream magazine delivery services 1 and 2 will increase in April, depending on the weight of an item. Presstream 1 will rise by up to 6.9% while Presstream 2 will increase by up to 5.9%.

"Each individual publisher will have to work out the precise impact, but no price increase is good news," said PPA director of circulation Nicola Rowe.

Potential mailsort prices 
Service: MS2120OCR
Average now: 17.4p
After rise: 18.2p

Service: MS3120OCR
Average now: 15.7p
After rise: 16p

Service: Cleanmail1 OCR
Average now: 27.6p
After rise: 28.8p

Service: Cleanmail2 OCR
Average now: 20p
After rise: 20.5p