The leaders of some of UK's largest businesses are accused of putting their own personal interests ahead of the country by backing Tory plans to reverse rises in National Insurance contributions (NICs).
Senior figures in the charitable sector, academia and politics warned that the interests of vast sections of British society were being ignored amid the hysteria generated this week by a roll-call of industrialists supporting Tory tax policy.
The fall-out from their intervention continued to dominate campaigning yesterday as clashes intensified between Labour and Tories over how David Cameron would afford his eye-catching promise and whether it would cost thousands of jobs.
Today, David Cameron will announce the latest element of his tax proposals with plans to give married couples a tax break of up to £150 a year. The move – designed to meet the Tory leader's promise to recognise marriage – is targeted at basic rate taxpayers.
But, amid signs of a backlash against the Tories and their supporters, Vince Cable, the Liberal Democrat Treasury spokesman, turned on the businessmen, whose numbers have risen to more than 130, accusing them of having mixed motives for backing the proposals.
"We are seeing extraordinary behaviour from the captains of British industry. Some of these businessmen have had massive increases in their remuneration and are paid a hundred times more than their workforce, yet they have signed up to an agenda based on voodoo accounting which they would never dream of employing in their own enterprises."
Caroline Lucas, the leader of the Green Party, said: "It's very depressing to see the debate dominated essentially by vested interests within big business doing what you would expect them to do – protect their bottom line."
The complaints were echoed by pressure groups protesting they were at risk of being drowned out of the election debate. Michelle Mitchell, charity director for Age UK, said: "We have heard a lot from the business lobby, but other groups such as older people are important too and their voices must be heard. Older voters have huge influence in this election and it is vital politicians listen and take action on the issues, such as pensions, social care, working in later life, which are important to them."
A spokeswoman for Gingerbread, the charity for lone parents, said: "Debates about tax and spending need to be conducted listening to the voices of those whom they will affect most. Half of all single parents live in poverty and decisions about where the money goes will have a major impact on their lives and those of their children."
Environmental groups also warned that the issue had been pushed to the margins of the election by the intervention of the big business lobby.
John Sauven, the executive director of Greenpeace, said: "It's quite bizarre that such a small group of people fighting over a relatively small amount of money has taken up such a large proportion of the election coverage."
A leading academic told The Independent last night it was rare for business leaders to become such active participants in election exchanges. Professor Tony Travers, of the London School of Economics, said: "It's unusual in recent times for so many business leaders to adopt a high public profile. They well know they are going to get dragged into politics; they don't mind that.
"My hunch would be that they have worked out that they are so important to the Government – because all job growth is going to be in the private sector – that whoever is in government is not going to mess with them."
The Tories were yesterday for the first time thrown on to the defensive in the row over their plans to reverse the NICs rise, which they say will be paid for by efficiency savings of £12bn.
Sir Peter Gershon, one of Mr Cameron's efficiency advisers, said up to £2bn would be raised by cutting the public payroll by an estimated 20,000 to 40,000 jobs. The Tory leader claimed that the posts could be shed by not filling vacancies as they arose and there would be no compulsory redundancies.
But Mr Brown said the Tory plans would lead to "substantial" job losses.