Unions predict a raft of unofficial strikes on the day war is declared.
Anti-war campaigners are calling for workers and students to stage a walk out when war breaks out.
Union general secretaries have not called for industrial action, but are looking at stepping up action at a special emergency meeting of the TUC's general council on Wednesday.
More than 100 senior unionists are due to meet, and will debate how to step up the pressure on the Government.
According to the Financial Times, the RMT transport union, the Public and Commercial Services Union and the Communication Workers' Union also expect walkouts by members on the day the war begins.