Ed Miliband would be a 'catastrophe' for Britain, according to FTSE 100 bosses . Seven out of 10 business chiefs at Britain's biggest companies think Ed Miliband would be a 'catastrophe' for Britain, a survey has revealed. The poll of FTSE 100 chairman has revealed overwhelming support for David Cameron to remain Prime Minister, despite the widespread business concern over his pledge to hold an in-out referendum on Europe. It comes just days after more than 100 company bosses signed a letter warning against a Labour government. It also echoes controversial remarks by the Boots chief executive Stefano Pessina who sparked fury after claiming it would be a 'catastrophe' for the UK if Labour won the election. The poll of 35 business chairman, by the headhunters Korn Ferry, is a further blow to Labour which is struggling to repair its relationship with big business after a series of controversial policy announcements. Mr Miliband last week vowed to ban 90 per cent of zero-hours contracts and  unveiled proposals to make it easier for workers to take their bosses to court for unfair dismissal. He also confirmed plans to raise corporation tax for the first time in 40 years to raise cash for a £400 cut in business rates for smaller firms. One of the FTSE 100 bosses surveyed, who did not want to be named, said businesses could work with Labour's shadow business secretary Chuka Umunna and its economics chief Ed Balls. But he said Mr Miliband's 'tone and rhetoric' had proved 'deeply disturbing', adding: 'At times his language is vitriolic and he appears to completely misunderstand business.' Mr Umunna, speaking on Radio 5 Live today, Umunna insisted Labour was no anti-business and defended Mr Miliband's recent announcemtn that Labour would all-but outlaw zero-hours contracts. Mr Umunna admitted not all zero-hours contracts were 'awful and bad', but insisted many workers were being exploited. Scroll down for video . Mr Miliband has vowed to force companies to offer staff a full time contract if they have been working regular hours for three months. Mr Umunna said: 'I think this will be massively helpful. There are 1.8million zero hours contracts now and I think this will transform people's lives.' The shadow business secretary has also pointed to Labour's refusal to offer a European referendum as a policy which business supported. David Cameron and George Osborne, out campaigning today, have jumped on business criticism of the Labour Party to boost their core campaign message that only the Tories can be trusted with the economy . He said: 'Business people have been very impressed that Ed took a decision on a matter of principle on the in-out referendum. It would have been easier to dance to Nigel Farage's tune, as the Conservatives have done.' Last week, Mr Umunna and a host of other Labour figures hit out at Britain's top business leaders after they backed the Conservatives' economic plan and urged voters not to risk a 'change of course'. In a highly unusual intervention just weeks from the general election, the business chiefs claimed a Labour government would 'put the recovery at risk'. Mr Miliband said the letter was not a surprise and only showed that the Tories were on the side of 'a few big firms and individuals at the top'. Mr Umunna, meanwhile, dismissed the signatories as a 'cosy little club', while Labour peer John Precott went further criticising them as 'tax dodgers, Tory voters and non-doms'. Mr Cameron, however, insisted the intervention was 'unprecedented' and claimed it sent a 'very powerful message'. The business chiefs who signed the letter run companies with well known retail brands such as Primark, Iceland, Ladbrokes and Costa Coffee. Bosses behind big name retailers, drinks and restaurants have backed the Tory economic plan, including (top row) Primark and Costa and (bottom row) Ladbrokes, Cobra, Tango and Iceland . Executives at consumer brands such as Cobra beer, Britvic, Silver Spoon, Kingsmill, Thorntons, Robinsons, Tango and London Pride are also on the list. Embarrassingly for Labour, the list of business chiefs includes several who supported the governments of Tony Blair and Gordon Brown. However, Mr Miliband said the letter only served to expose the choice at the election. He said: 'Businesses have come out today to say they want lower business taxes and, you know, that doesn't surprise me. 'But it does also go to the wider choice at this election. The Conservatives really believe that if all of the few corporations and individuals at the top are doing well, the wealth will magically trickle down for everybody else. 'We have tried that experiment over the last few years and it hasn't worked. We have seen falling living standards and falling wages and insecurity at work. I just have a different view about the way the country succeeds.'
Poll of FTSE 100 bosses reveals overwhelming support for the Tories .
Seven out of 10 said Ed Miliband fearful of a Labour Government .
Comes after 100 business chiefs signed an open letter in support of Tories .
Mr Miliband said letter only showed PM backed his rich friends in the City .