Last month, BPIF members informed Unite that they would not discuss a national pay agreement for 2011, all but killing the possibility of the deal, which was last agreed in 2008, being resurrected.

Individual chapels have been left to negotiate with employers themselves, but the union has said that any pay claim should take into account the Retail Price Index (RPI).

A letter sent out to 1,121 union branches by national officer Steve Sibbald said: "Unite members working under the agreement have already made sacrifices to help employers sustain their business.

"Our claims have always used the RPI as a guide for reasonable settlements. The BPIF position in 2009 was that as the RPI was in the negative there should be no increase. Following the BPIF's logic, the claim should be an increase in wages of 5.1%, which is the current RPI."

The union has also claimed that some companies had "used the recession to needlessly drive down pay and conditions".

It has also sent out information regarding pay increases that have already been achieved in other industries in 2011. It claims that just two of pay settlements reached so far have been below 2%, with the median average 2.6%.

According to Unite statistics, Network Rail agreed a 5.2% increase, Bentley Motors in Crewe negotiated a 4.75% increase and Shell UK Oil in Stanlow agreed a 4.6% increase.