Return of the militants: Days lost to strikes have soared 20-fold in a year

The number of days lost to industrial action has risen almost 20-fold in the last year, demonstrating the growing readiness of union leaders to flex their muscles.

Prison officers went on strike last August, tube workers in September and train and postal workers in October.

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Strikes are also being considered by teachers, prison officers and staff at HM Revenue and Customs.

Figures from the Office of National Statistics show that 610,000 working days were lost in the public sector between July and November last year, compared to 32,000 over the same period in 2006.

The Conservatives have blamed the financial link between Labour and the unions.

Last night the Tories called on the Government to stop giving millions of pounds of taxpayers' money to the unions.

The handouts are in return for the unions "modernising" their activities.

The Department for Business, Enterprise and Regulatory Reform has already handed out £5.8million of a total £10million of taxpayers' money via the Union Modernisation Fund.

Two grants went to the Communication Workers Union, whose strike action against Royal Mail helped paralyse British business last autumn.

It accounted for 326,000 of lost work days last October.

The Transport and General Workers' Union - which recently voted on strike action - received funding to help it build links with the Polish Workers' Association.

Conservatives have also questioned Labour's willingness to bow to the unions' demands on legislation, including softening up strike laws and extending rights for agency workers.

Tory business spokesman Alan Duncan said: "The uncomfortable truth is that the unions have this Government over a barrel. Without trade union cash, the Labour Party would collapse.

"Gordon Brown should suspend the Union Modernisation Fund until we can see an end to the suspicious symmetry between receipts to the Labour Party and handouts from the Government."

Trade union money accounts for around three-quarters of Labour's funding.

In the last 12 months, the unions have donated £9million to Labour, which appears to have rescued it from bankruptcy.

Minister for employment relations Pat McFadden said: "Labour governs in the interests of the whole country, not of any single interest.

"Trade unions are part of our economy and the Union Modernisation Fund is about ensuring they too can modernise for the future."