UNIONS have declared employers emboldened by the aggressive industrial tactics of Qantas.

But business groups blamed the increasing aggression of companies on unions increasingly resorting to premature industrial action to try to pressure employers to cave in to unreasonable demands.

Schweppes yesterday denied union claims their popular soft drink brands could be in short supply at Christmas after the company locked out 150 workers indefinitely at its Tullamarine operation in Melbourne.

Schweppes took the action after the union imposed a series of one-hour rolling stoppages designed to disrupt the plant operations and pressure the company into abandoning plans to move from eight- to 12-hour shifts.

The employees union, United Voice, said Schweppes had conceded in court papers the supply of soft drinks could be interrupted over Christmas. The company said it had engaged non-union contract labour to work at the plant during the lockout.