According to Unite regional officer Steve Ireland, members rejected the offer at the end of December, before management disputed the result and refused to move forward with the agreed negotiating process.

He said: "During this time, several union members complained of having been approached by at least one member of the management pay negotiation team to ask which members of staff had been present at the union meeting in December, and how many had voted."

"‘In addition, management have put on hold any career performance salary increments and have stated they will do so until the pay discussions are resolved. Such a move has been widely viewed as an attempt to divide staff and pressurise union members into accepting a deal they rejected."

However, Cambridge University Press’s management team has said that the 2% offer is in line with the industry, with talks ongoing.

Andrew Gilfillan, managing director for Europe, Middle East and Africa, said: "We feel that a 2% increase for staff is reasonable, and is fully in line with industry, national and local pay settlements.

"Taking into consideration the future investment needed at the press and the uncertainties of the current economic climate, we believe that awarding more than a 2% increase in basic pay would be irresponsible."

He added that staff already benefited from a bonus scheme based on the press’s annual business results, which recently paid all eligible staff 4.2% of their earnings in the 2010 financial year, and which could pay between 3% and 6% in the current financial year.

Many staff are also expected to receive salary increases of 2.5-3% based on skills development.

Unite claims that CUP’s results last year indicate the company is doing well enough to warrant the increase.

The dispute comes just over two years after the parties clashed over proposed redundancies at the site.