THE Tories have been accused by trade unions of “betraying” the legacy of the Magna Carta by planning to restrict the fundamental human right to strike.

Prime Minister David Cameron will lead today’s jamboree marking the 800th anniversary of the signing of the charter.

But the TUC said his government’s plan to impose strike ballot thresholds were a “stain” on its legacy and the Star revealed in April that lawyers believe that the Tories’ proposals would breach International Labour Organisation conventions.

Public-sector union Unison leader Dave Prentis said yesterday that he was prepared to take the Tories to court.

Mr Cameron faced the revolt as he headed to Runnymede in Surrey, where King John was forced the Magna Carta in 1215 to appease land-owning barons.

Speaking at the site, the PM will pledge to uphold its principles of liberty, justice, democracy and the rule of law.

“It falls to us in this generation to restore the reputation of those rights — and their critical underpinning of our legal system,” he will say.

But TUC general secretary Frances O’Grady said that Tory policies did not match the PM’s hyperbole.

“On the day when we rightly celebrate human rights and access to justice, our government is busy working on reforms aimed at shutting down dissent and weakening people’s rights at work,” she said.

A 50 per cent turnout threshold on all strike ballots is among proposals in the Tories’ Trades Unions Bill, while strikes in “essential services” must have at least 40 per cent support of everyone eligible to vote.

Even when workers beat those barriers, the Bill would allow bosses to break strikes with scab labour and criminalise strikers if there are more than seven people on a picket line.

Ms O’Grady described the laws as an “opportunistic and ideological” attack on unions designed to “suppress” dissent to further public-sector job cuts.

“Magna Carta laid the ground for the fundamental rights and institutions that we have today,” she said.

“These plans are a stain on the spirit of Magna Carta and an affront to that solid British notion of fair play. These reforms must be shelved.”

An International Labour Organisation spokesman told the Star that the UN body would investigate whether the Tories had breached international law if a complaint was made by a British union.

Mr Prentis said Unison would challenge the “vindictive” laws.

“We are gearing up to resist the attacks on trade unions with every means at our disposal, and if necessary we will take legal action,” he told reporters.