Labour’s poll ratings have hit a four-year low as Ed Miliband faced fresh criticism from party grandees.
The latest in a series of YouGov studies putting the Conservatives ahead saw Labour on 33%, the party’s lowest figure with the pollster since June 2010, before Mr Miliband’s election as leader.
The poll put the Opposition two points behind the Tories, and came as a series of influential figures attacked the plan for a “mansion tax”.
The YouGov survey for the Sun put the Tories on 35%, Labour on 33%, Ukip on 13% and the Liberal Democrats on 8%.
Pressure is mounting on Mr Miliband over his leadership after more influential figures in the party took a swipe at his election strategy.
The Labour leader is struggling to gain the political momentum and his conference speech, during which he failed to mention the deficit, has appeared to clear the way for critics in the party to speak openly.
Concerns have been raised about plans to introduce a mansion tax on properties worth more than £2 million.
Margaret Hodge, chairman of the powerful Public Accounts Committee, told the Times it was “too crude to work properly”.
She said: “I don’t think it’s the world’s most sensible idea. We need to tackle the idea that people are shielding their money in London through properties.
“The problem identified is the right one; I just think the solution is too crude to work properly.”
And former cabinet minister Dame Tessa Jowell told the newspaper: “I am concerned about typically older families who are asset-rich and income-poor.
“They bought houses 40 years ago, which have appreciated enormously in value, and they certainly can’t afford a mansion tax.
“The important thing is we set out how it will be applied and the fairness test that will apply.”
It comes after the Labour leader was accused by party grandee Lord Prescott of showing a severe lack of ambition in a damning assessment of his “far too timid” strategy and underwhelming conference performance.
Prominent Labour donors also raised concerns over the weekend, with Lord Noon, one of the party’s significant individual benefactors, saying the party “really need to buck up” and Lord Levy, who was Tony Blair’s chief fundraiser, criticising the tax plans as “totally inappropriate”.
One of Labour’s biggest individual donors, JML founder John Mills, told the Huffington Post the mansion tax could push people into negative equity.
“The problem with the mansion tax - apart from issues of whether it’s fair or going to work - is it requires really tricky valuations,” he said.
“It’s a step from zero to some quite large number which is going to produce all sorts of problems on the boundary. If people have got mortgages, they could get into negative equity. There are these sort of problems as well.”
Meanwhile, shadow chancellor Ed Balls said he was “surprised” that Mr Miliband had forgotten the economic section of his keynote conference speech.
He told ITV1’s The Agenda: “Sometimes in life you can forget the most important things. In that speech, not talking about the deficit.”
The latest YouGov poll follows research by Conservative pollster Lord Ashcroft yesterday which put Labour two points down on 30%, behind the Conservatives who were unchanged on 32%.
A survey by Populus, however, put Labour on 37%, ahead of the Tories on 31%, Ukip on 15% and the Lib Dems on 8%.
• YouGov interviewed 1,739 British adults online on October 5-6.