Two Labour donors have waded into the ongoing conflict between the Labour party and the business community, criticising Labour leader Ed Miliband for his “unnecessary” assault on commercial enterprise, and warning that the stock market will tumble if Labour win the general election. The battle has been so damaging to the party that Tony Blair has offered to step back into the fray and take on an official campaigning role in the run up to the election.

The feud was ignited eight days ago by Boots boss Stefano Pessina who said that a government led by Ed Miliband would be a “catastrophe” for Britain, adding that Labour’s plans should they take power are “not helpful for business, not helpful for the country and in the end it probably won’t be helpful for them”.

Mr Miliband immediately struck back, focusing on tax avoidance over which he insisted “I am not going to back down. The time has finally come to put an end to a society in which one group of people can play by different rules to the rest.”

The feud has been smouldering on all week. Today, two of Labour’s most successful former business backers, Lord Haskins and Lord Paul attempted to throw cold water over the flames by telling the Telegraph that the row was “unncessary” and “not sensible”.

“If you go into a situation before the election and there is such bad will between business and the Labour Party, and the Labour Party wins the election, then you get all sorts of upheavals in the stock market shortly afterwards, which is very unsettling,” said Lord Haskins, the former chairman of Northern Foods. “Therefore it is not sensible for the Labour Party to go out after the business community.”

He described plans for an energy price freeze as a “half-baked scheme” which had to be re-written after prices fell. “The mansion tax is another nonsense,” he said. “It’s another half-baked scheme which will be extremely difficult to enforce and it won’t deliver anything like what they expect it to. It will pull a lot of people who aren’t very rich into it, particularly in the south-east of England. Those are not very sensible policies by Labour.”

Meanwhile Lord Paul of Marylebone, who gave £400,000 to New Labour and was close to Gordon Brown told the Telegraph that he was “really shocked” by the row. “All I know is, irrespective of who forms the government, they cannot afford to see business being destroyed.

“I don’t think the Conservatives have done any great job for business, nor that Labour is going to make it any worse. My view is that if they [Labour] get into power they have to make sure business survives otherwise it doesn’t help their own people because they need jobs also.”

Lord Paul sits as an independent peer, having left the Labour benches in 2010. He says he is still in my heart a Labour man”, but thinks that politics has become too “dirty”.

Commenting on Mr Miliband’s description of some companies as “predatory”, Lord Paul said “These are all modern terms. I think this whole debate is going very wrong. I wish we could get back to the real [political work] of trying to win votes on your merit.”

Chris Wright, founder of the music publishing giant Chrysalis also lined up to criticise Miliband’s stance, waring that Labour was risking stoking the “politics of envy” which would be damaging to Britain’s economy.

Wright was one of 63 prominent businessmen who backed Labour in the run-up to the 2005 election, but last night told the Times that he would “not sign a similar letter today”, adding “In the current Labour leadership, there’s a vein of thought that is to some extent anti-wealth creator and anti-business and that is a great shame.”

And Chris Gibson-Smith, chairman of the London stock exchange, has also criticised Labour’s rhetoric on the mansion tax and the energy price freeze. “They all look like retrograde debates, going back to the Seventies,” he said.

Meanwhile, with Labour proving unable to pull decisively ahead in the polls as we edge nearer to the general election, Tony Blair has offered to help with the party’s campaigning efforts. The Observer has reported that talks have been going on for weeks between Blair’s office and the Labour party over what role he might assume during the run up to polling day.

When asked whether Blair was prepared to support the party’s campaign, a spokesman from his office said that, regarding “his involvement in the party’s election campaign, he will do whatever the party wants”.

In addition, Blair’s former spin doctor Alistair Campbell is known to be heavily involved in preparign Mr Miliband for the televised leaders debates due to take place, while Peter Mandelson has also publically stated his support for Miliband, saying that he would “make a very good prime minister” and was not anti-business.

A poll carried out this week by YouGov for The Sunday Times found that 43 percent of voters agree a Labour victory would be bad for British business, against just 19 percent who think it would be good. More than half of voters, 52 percent, think business leaders’ attacks have been damaging to Labour.