Mr Rorris said a resolution at a labour council meeting on Wednesday had thrown the support of the council's 29 affiliates and 20,000 represented workers behind the Tahmoor miners.

"The unions of the South Coast are standing solidly behind the Tahmoor miners," he said.

As miners tried to shelter from the day's heat during their third day manning a picket line outside the colliery, Mr Rorris expressed disappointment at Xstrata's choice to lock out workers until Monday, and warned there would be consequences if the company maintained its present course.

"Lockouts are a very, very ugly tactic. If the multinational wants to continue down this really ugly course of action, they'll not only have to answer to the miners but to all the workers of the South Coast," he said.

Xstrata had previously indicated it considered the lockout to be a reasonable response to continuing industrial action.

Xstrata Coal communications manager James Rickards said the union's demands were inconsistent with industry standards.

"The CFMEU are demanding a 2010 pay increase for 1980s restrictive workplace conditions. This is not in the interests of our people or the viability of the operation, and is significantly out of step with the rest of the industry," he said.

NSW Fire Brigades Employees' Union president Darin Sullivan said his members would join the picket line today.

"Our intention is really to offer that solidarity and let them know that other unions are there for them," he said.

A CFMEU spokesman yesterday afternoon said miners would remain on the picket line "for the long haul".