Fletchers EQR says reducing what it pays painters will not lead to a retreat of tradespeople from the rebuilding of Canterbury.
The company, which is contracted by the Earthquake Commission to do the work, has dropped the square metre rate from $25 to $19.
Canterbury Master Painters Association says many will probably give up doing work for Fletchers EQR, and this will lead to less qualified trades people being hired.
Council of Trade Unions president Helen Kelly says Fletchers is taking advantage of the people rebuilding Christchurch to boost its own profits.
Ms Kelly says workers should have a say in their pay and conditions and she's urging painters and plasterers to demand the rate be put back up.
Ms Kelly is also calling on the Earthquake Commission to bring the company into line.
Fletchers EQR says there will not be an exodus, as workers are being paid a fair market rate.
A company spokesperson says the painters' rate was changed to keep it at market levels and the quality of painting work will not drop.