Greek private sector workers will stage on December 1 the first major strike since a national unity government took over, signalling that labour unions will not soften their stance against austerity policies under the new coalition.

GSEE, the country's umbrella trade union representing about 2.5 million private sector workers, called the 24 hour strike on Tuesday to protest against the 2012 budget, which is scheduled to be approved by parliament on December 7.

The strike is against this budget of austerity and social spending cuts, said GSEE spokesman Stathis Anestis.

Passing the 2012 austerity budget is one of the conditions for receiving a 130 billion euro bailout from the country's international lenders.

Public sector trade union ADEDY, which represents about 500,000 state employees, will decide later on Tuesday if it will join the walkout.

The 2012 budget includes a series of tax increases and spending cuts to ensure the budget deficit falls to at least 6.7 percent of GDP next year from 9 percent in 2011.

Both Greece's major parties, socialist PASOK and conservative New Democracy, said they will back the budget.

The coalition government led by former European Central Bank vice president Lucas Papademos, which took over earlier this month, submitted the budget last week.

(Reporting by Harry Papachristou; editing by David Stamp)