Ministers are reportedly considering moves to crack down on the unions amid fears of a wave of crippling industrial action over public sector cuts.
Business Secretary Vince Cable and Cabinet Office minister Francis Maude are drawing up plans that could see an end to full-time union officials receiving taxpayer-funded salaries, according to The Sunday Telegraph.
They are also looking at the possibility of legislation imposing a minimum threshold on strike ballot turnouts before industrial action can be taken, the paper said.
The prospect of such a package, described as a "last resort" by a source, comes as relations between the Government and union leaders is turning increasingly bitter over plans to reform public sector pensions.
Prime Minister David Cameron is expected to make a speech defending the plans which will require public sector employees to work longer and, for most, pay more into their pension pots for often less attractive benefits.
His intervention follows a series of warnings from Cabinet ministers, including Dr Cable, about the likely consequences of union militancy.
Earlier this month the Business Secretary told the GMB's annual conference that pressure for a change to the strike laws would "ratchet up" if the unions caused economic damage with industrial action.
Chief Secretary to the Treasury Danny Alexander infuriated the unions last week by warning it would be a "colossal mistake" to reject the Government's offer on pensions, which he said was the best they could hope for.
However strikes will begin on Thursday when up to 750,000 teachers, lecturers, civil servants and other public sector workers take action and there are threats of further walkouts throughout the summer and autumn.
RMT general secretary Bob Crow said the unions were on the edge of "the biggest industrial confrontation in 80 years" and warned of the biggest counter-operation since Margaret Thatcher's government in the 1980s.
Photo by bisgovuk, Press Association