A number of strikes will be launched by thousands of workers across the rail, post and airline industries in the lead up to Christmas this week.
Workers at Southern Railway, Post Office and British Airways are all set to strike.
Members of the Rail, Maritime and Transport union at Southern are striking on Monday and Tuesday, causing fresh chaos for the franchise's 300,000 customers.
Meanwhile, members of the Communication Workers Union will strike for five days - including Christmas Eve - at the Post Office.
British Airways cabin crew in the Unite union are due to strike on Christmas Day and Boxing Day in a row over pay.
Many of the strikes are part of disputes over issues such as jobs, pay, pensions and safety.
Officials dismissed, however, that the strikes were co-ordinated or part of a conspiracy to bring down the Government.
Southern Rail strikers are in a dispute over the role of conductors.
Post Office workers are striking over job losses, the closure of a final salary pension scheme and the franchising of Crown Post Offices.
British Airways staff will walk out over pay issues - although talks could help divert the strikes.
RMT general secretary Mick Cash said: "We are a serious trade union dealing with serious issues around safety on the railways. That is our absolute priority.
"RMT is not party to any Trotskyist conspiracy to bring down the Government.
"Our conductor members on Southern are on strike this week in defence of the safety of the travelling public and that remains the focus of the entire union."