The are planning the biggest crackdown on strikes since Margaret Thatcher's era by bringing in new criminal offences for "illegal picketing", imposing time limits on mandates, increasing the notice period for employers and insisting that 50% of union members vote in ballots that approve industrial action.In its general election manifesto, David Cameron's party will introduce sweeping changes aimed to make it more difficult for workers to go on strike. A walk-out by up to a million public sector workers last week led to strong signals from the prime minister that he would back much tighter strike laws – a key demand of Boris Johnson, mayor of London. branded Cameron a "Bullingdon bully" and pointed out that politicians are elected on much lower turn-outs than 50%. Unite, Labour's largest financial backer, also released a Survation opinion poll suggesting that some of the union-bashing rhetoric of the 1970s and 1980s no longer instantly chimes with the public mood. The survey found the public backed the right to strike in the latest dispute by 61% to 31%, supported a £1-an-hour increase in council workers' wages by 48% to 35%, and opposed public-sector real-terms pay cuts until 2018 by 56% to 25%.However, the Conservatives believe the promise to make it more difficult for workers to strike will appeal to their potential voters. Under the new measures due to be outlined today, the party will say they would:• Introduce a 50% turnout threshold for strikes. This will effectively mean any strike will need a double majority to be lawful: an absolute majority of those eligible to vote participating in the ballot and a simple majority in favour of industrial action.• Reform picketing rules to make the current code of practice on pickets legally binding, and make illegal picketing a criminal offence. This would not take away the right to picket, but it would limit how, where and why picketing can take place. The Conservatives claim they want to "better protect those who want to come to work".• Force unions to provide specific details about the nature of the dispute and a requirement to vote on each aspect of the dispute. It would also require unions to set out clearly the form of the proposed action on the ballot paper (eg time of year, length).• Extend the notice period unions are required to give employers from seven days to 14 days before industrial action.• Remove the requirement to trigger action within four weeks of a ballot and set a firm time limit of three months on the duration of the mandate.Francis Maude, the cabinet office minister, said he had previously warned that the more union leaders "pushed for disruptive strike action without even persuading a majority of their members to vote, the stronger the case would become for changing the law".He said: "This sensible and proportionate package of reforms will help protect hardworking families and British businesses as part of our long-term plan to build a stronger economy".Last week, Len McCluskey, the Unite general secretary, attacked the prime minister's plans to tighten the strike laws."The whiff of hypocrisy coming from Cameron as he harps on about voting thresholds is overwhelming," he said. "Not a single member of his cabinet won over 50% of the vote in the 2010 election, with Cameron himself getting just 43% of the potential vote."If he practised what he preached then no Tory councillors would have been elected in the last 20 years and Londoners would have been spared the circus of Boris Johnson. So we'll take no lessons from the Bullingdon bully,Discount Ray Ban Eyeglasses, who gives tax breaks to his City chums yet plots to deprive lowly waged workers of their right to fight poverty pay."