Visiting the Eastleigh by-election, Miliband said he would be tabling a motion in the Commons to introduce the levy in the hope of pushing it into Chancellor George Osborne’s March Budget.
Miliband also made a direct call to Liberal Democrat leader and Deputy Prime Minister Nick Clegg to back Labour’s call, noting the policy has been supported widely by his party.
The Labour leader confirmed his support for the tax last week in a speech in which he also revealed Labour would reintroduce the 10p income tax rate to benefit low earners.
It would be paid for, he said, by the “mansion tax” – a 1 per cent tax on the extra value of any house above the £2m threshold. It would mean the owner of a £2.5m home paying an extra £5,000 every year.
The by-election – to be held on 28 February – was called after the resignation of disgraced Lib Dem MP Chris Huhne, who was found guilty of perverting the course of justice in a speeding case earlier this month.
Miliband said: “The big question today is for the Liberal Democrats. We have said we will table a motion before the Budget [on 20 March] to introduce a mansion tax. They have said they are in favour of that. I say to him ‘tell us you will vote with Labour to force George Osborne’s hand and force him to introduce a mansion tax’.”
Miliband said Lib Dem pledges that “behind the scenes” deals would persuade the Conservatives to introduce such policies had not worked over the three years of the coalition government. He said, as a result, the party had become an “accomplice” to the Conservatives. “Let’s see that at least on this he [Clegg] has got the courage of his convictions,” said Miliband.
With support from the Lib Dems and other smaller parties, the Commons could find the numbers to pass such a tax. However, the Lib Dems gave the idea a frosty response last night, saying a Commons vote on the issue would throw Osborne’s Budget preparations into chaos.
Stephen Williams, the party’s Treasury spokesman said: “They [Labour] are doing just silly politics. This is the sort of thing that does not appeal to the public.”
Chief Secretary to the Treasury Danny Alexander also said that Labour had not said what form its mansion tax would take.
Miliband’s call came as all three main parties swamped Eastleigh ahead of the by-election. Labour is in third place, but has seen its odds shorten massively following the decision by author and satirist John O’Farrell to stand.
Miliband said: “This is a living standards by-election, that’s the issue on the minds of so many people in Eastleigh – not being able to afford the weekly food bill, not being able to afford to fill up the car.”
There was also a row sparked by the Conservative candidate Maria Hutchings after she appeared to suggest that her son would need private schooling to achieve his dream of a top medical career.
“William is very gifted, which gives us another interesting challenge in finding the right sort of education for him – impossible in the state system. He wants to be a cardio-respiratory surgeon, she said.
Opposition parties said she had “insulted” state schools in the seat, but the Conservatives said she backed reforms to the English secondary school sector, being introduced by Michael Gove, to boost standards.
Yesterday, Osborne was at a G20 finance ministers meeting in Moscow, where it was agreed to crack down on tax avoidance by multinational companies.
The final communique said members were determined to develop measures to stop firms shifting profits from a home country to pay less tax elsewhere.