Uncoated mechanical grades could increase by £25-£40, with the increases effective from 1 January 2011 and most prices firm only until 31 March 2011.

One industry source said he had received price increase letters from UPM that "make clear" increases of £50 per tonne in coated mechanical papers, and £30 per tonne on uncoated mechanicals.

UPM general manager Will Oldham said: "The picture on price increases is complicated but most of the activity is focused on publication grades where, depending on the term of the agreement being renegotiated and the particular grade, increases vary from 8-25%."

Another senior buyer said he had received letters citing increases for medium- and lightweight coated grades.

He said: "The price increases are out of kilter with the economy and mean that we can’t budget for the magazines. The mills are blind to that and think that the market can withstand it.

"It shows a massive lack of understanding. They are very, very bullish and have an attitude of ‘take it or leave it’."

Marco Eikelenboom, sales and marketing director of graphic papers at Sappi, said the company was "currently undertaking an effort to raise mechanical coated prices".

Both SCA and Stora Enso declined to comment on the proposed increases, while Norske Scog was unavailable as PrintWeek went to press.

For more, read PrintWeek's analysis here