Conservatives will legislate to make it more difficult for unions to call strikes in key public services if they win this year's election.
Industrial action in the health, education, transport and fire services would require the support of at least 40% of all those entitled to take part in strike ballots - as well as a majority of those who actually turn out to vote.
A Conservative source said this would prevent strikes going ahead on the basis of majorities in ballots in which only a small proportion of the unionised workforce has participated.
The move was denounced as a "democratic outrage" by the TUC, who said it would effectively end the right to strike in the public sector at a time when Conservatives are planning pay restraint and large-scale job cuts.
GMB general secretary Paul Kenny pointed out that Conservatives failed to secure 40% support of those who voted in the 2010 general election, while only 15 Tory MPs had the backing of 40% of those entitled to vote in their constituencies.
Under proposals to be included in the Conservative manifesto for the May 6 election, Tories also pledged to end the ban on the use of agency staff to cover for striking workers, and promised a review on the possible introduction of minimum service levels to ensure that core services remain available during strikes.
Civil servants are to join a huge public sector strike over pay on July 10 after voting to support industrial action, the Public and Commercial Services union said.
The possibility of a massive strike across the public sector could come closer when a leading trade union reveals the results of a strike ballot today.
The Unite union will announce the result of a vote by its 70,000 members who work in local government in England, Wales and Northern Ireland.
Unison and the GMB have already held ballots with their members voting in favour of industrial action over the Government's decision to limit pay rises to 1%.
Their members will take part in a one-day strike on July 10th, but the participation of Unite members would add to the challenge to the Government's policy of limiting public sector pay rises.
Thousands of civil servants will stage strikes over the next three days as part on an ongoing campaign of industrial action in a row over pay, pensions and conditions.
Members of the Public and Commercial Services union (PCS) at public and regulatory bodies including Ofwat, Ofgem, the Food Standards Agency and the Equality and Human Rights Commission will walk out for an hour from 11am today, tomorrow and Friday.
A walkout by Public and Commercial Services (PCS) union members is set to hit workplaces across the UK this afternoon.
Starting at 1pm, PCS members will take part in a half-day strike to tie in with a three month campaign over pay and pension disputes.
PCS general secretary Mark Serwotka said: "These walkouts, following our strike on budget day, are part of an ongoing campaign of industrial action and protests to put pressure on a government that is refusing to even talk to us.
"We have asked for talks but ministers and senior officials have refused, so we are taking action to oppose and shine a light on what are deeply unfair and unnecessary cuts to the living standards of hard-working public servants."
In response to today's strikes at more than 300 crown Post Offices nationwide, the Post Office issued the following statement:
"Crown branches are currently losing £40 million per year and this is being subsidised by public money.
This cannot continue. We are committed to the Post Office remaining a key part of UK high streets and our plans ensure this will happen."
As well as opposing branch closures, the CWU are also demanding an end to pay-freezes for its members.
And stress that unless an offer is forthcoming, more industrial action could be on the cards."
The Communication Workers Union (CWU) claims that plans to close or franchise 70 of the UK’s biggest post offices - known as the Crown network - will affect hundreds of jobs.
Dave Ward, the CWU's deputy general secretary, said, "Our Post Office members are standing up against destructive plans which would slash 20% of the Crown network and are simply asking for fair treatment and job security.
"The Post Office's plans are short-sighted and would rob the network of the most productive offices while simultaneously putting hundreds of jobs at risk and potentially damaging local economies.
“We'd like to see a better vision for a successful network which maintains services in the heart of communities alongside quality jobs.
"We're confident this could be achieved if Post Office management would agree to negotiations".
Civil servants will stage a 24-hour strike on Budget day today, in a row over pay, pensions and working conditions.
It is thought up to 250,000 members of the Public and Commercial Services union (PCS) will join the walkout, which will hit job centres, border control at airports, tax offices and courts.
A half day of action has also been called on April 5th, as part of a three month long campaign of action.
Picket lines will be placed outside government offices, museums, galleries and the Houses of Parliament.
Civil servants have planned a second walkout in a row over pay, following their Budget day strike.
Almost 250,000 members who work in government departments and its related bodies will hold a half-day walkout on April 5, the Public and Commercial Services union said.
A 24-hour stoppage has been called by the union on Wednesday after accusing the Government of refusing to negotiate over cuts.
A three-month programme of industrial action is also being planned, along with a fresh campaign against tax avoidance and evasion.