Labour will today launch a hard-hitting campaign against David Cameron's proposal to repeal the ban on hunting with dogs. The move will be seen as an extension of its "class war" against the Conservatives. Ministers will point to Mr Cameron's record of supporting fox-hunting and condemn his proposal to give MPs the chance to overturn the Hunting Act if he becomes Prime Minister.

Writing in The Independent today, the Environment Secretary Hilary Benn says: "Quite why this is something that would be a priority for a Tory government, instead of the economy or tackling other concerns, is hard to explain to the public and [the Conservatives] have failed to do so."

Last night, Mr Benn explained: "David Cameron used to hunt foxes. He talked about fox-hunting in his first speech to Parliament, and he has said that if he becomes Prime Minister he will get rid of the fox-hunting ban.

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"But like the vast majority of people, I think the barbaric act of letting dogs tear foxes to pieces should not return to our countryside. If you think the Tories have changed, their views on fox-hunting with dogs make it absolutely clear that their priorities haven't."

Supporters of hunting will be out in force today – traditionally a big day in the hunting calendar – to press for the repeal of the Act. But Labour's decision to launch the "back the ban" campaign makes clear that the party will make hunting an issue at next year's general election. Although Mr Benn insists hunting is not a "class issue", the move follows Gordon Brown's attack on Mr Cameron's plans to cut inheritance tax, which he said were "dreamed up on the playing fields of Eton".

One senior Labour source said: "We are not saying hunting will be the centrepiece of our election campaign. But it is an issue that concerns many people and it says something about the Conservatives. They say 'we are all in it together' but their policies, whether on inheritance tax or hunting, show that under a Cameron government there would be one rule for their friends and another for the rest of us."

When Labour's focus groups remind voters of the Tories' stance on hunting, many people are said to reply: "I guess they haven't changed." People are surprised that Mr Cameron wants to overturn the ban, and Labour believes the policy undermines his claim to have modernised the Conservative Party.

However, some Blairites are wary of Labour's "class war" attacks, which they fear will undermine the party's support among the aspirational middle classes and give the impression that Labour is appealing to its "core vote" in the hope of denying Mr Cameron an overall majority.

A "Tory toffs" campaign in last year's Crewe and Nantwich by-election backfired on Labour, but Brown allies insist that the new drive is legitimate because it is linked to Tory policies, not personalities.

The "back the ban" campaign will be endorsed today by the television presenter Tony Robinson and actors Patrick Stewart and Jenny Seagrove. Its survey of parliamentary candidates found that 84 per cent of Tories who responded did not support prohibition of hunting with dogs, but 98 per cent of Labour candidates did.

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The emotive campaign will challenge Tory parliamentary candidates to make public their positions on hunting. Labour activists and hunting opponents will be told: "Find out what your MP and candidates think about allowing foxes to be ripped apart by the teeth of hounds."

Amid signs that the Tories are playing down the issue, their candidates are said to have been advised not to state their view on hunting but to promise to consult their constituents before deciding how to vote. The Tory manifesto will promise a free vote on a government rather than a private member's Bill, a move which guarantees parliamentary time and would make it harder for opponents to block. If the Tories win an overall majority, the Commons is expected to overturn the ban.

The 2004 Act made the hunting of all wild mammals using dogs an offence and banned hare coursing, but did not stop people from riding with their dogs if they remain within the law. The Tories insist the Act is ineffective and unworkable. They say there have been few successful prosecutions and that such a bad law should be repealed.

In February Mr Cameron said: "My personal view has always been the ban doesn't work, it doesn't make sense. It's an area of life that I don't think the law ought to go into. It doesn't seem to have worked in any way."

*The Charity Commission has banned a "keep cruelty history" newspaper advertisement planned by the League Against Cruel Sports, which opposes the repeal of the Act.

According to Whitehall sources, the commission ruled that the advertisement – which highlighted the words "cruel Tory" in blue type – would have breached charity rules that ban party political campaigns.

Hunting ban What impact has it had?

*Despite the ban, more than 300 hunts are expected to meet today, on the biggest day in the hunters' calendar.

*The law permits them to chase their quarry across country, provided the hunt does not end with a fox being torn to pieces by hounds. Any form of hunting with dogs, including hare-coursing and deer stalking, was banned under the 2004 Hunting Act. The Conservatives have promised that if they will next year's general election, they will give MPs a free vote on whether to repeal the Act.

*The RSPCA has released figures which, it says, show that the Hunting Act has proved to be an effective piece of legislation. There have been more prosecutions under the Act than under similar legislation on animal welfare, and more than three-quarters of the prosecutions have been successful. Last week, the European Court of Human Rights rejected a claim that the Act was a breach of human rights.

*But research carried out by the Countryside Alliance shows that 57 per cent of the public believe that the Act is a failure, and nearly half think that a new government should either repeal it or give Parliament a free vote on whether to keep it.