The TUC has called on the CBI to back measures aimed at "naming and shaming" companies that fail to pay their workers the minimum wage.
The union call comes as the CBI publishes its submission on the subject to the Low Pay Commission later this week. In it, the business organisation concedes that the minimum wage has benefited lower-paid workers.
But it also warns that another substantial rise would "damage many businesses and boost the black economy".
"Continuing heavy annual increases are simply not sustainable, as the Low Pay Commission itself acknowledges," said Susan Anderson, the CBI's director of human resources policy.
"Firms are already under great pressure from rising energy costs, lower-wage competition overseas and an uncertain global economic outlook. Others are being undercut by a minority which take workers on the black market to avoid paying the minimum wage.
"We hope that this year the rise will be more modest."
The latest increase comes into effect next Sunday, when it will go up to £5.35 a hour. Since its introduction in 2002, the minimum wage has grown 27 per cent.
In contrast to Ms Anderson's position, TUC general secretary Brendan Barber said that, given the "positive economic outlook", achieving a minimum wage of more than £6 by 2008 should be "easily affordable".
"The CBI is right to attack bad bosses in the cash-in-hand economy who undercut good employers by paying as little as £1 per hour," he said. "But it needs to go further. I look forward to employer groups supporting our calls for tougher enforcement of the wage, including the naming and shaming and even imprisonment of rogue employers."
The TUC listed its range of suggested measures in its own submission to the Low Pay Commission earlier this month.Reuse content