Brown engages in class warfare as Cameron forced on the defensive

According to the Duke of Wellington, Waterloo was won on the playing fields of Eton. If Gordon Brown gets his way the English public school will be the battleground for the coming next general election.

Prime Ministers questions today degenerated into raw political knockabout in which Mr Brown retreated to his comfort zone of class warfare, notably mocking David Cameron's public school background.

Mr Brown was back on the offensive after a difficult couple of weeks for Mr Cameron. The clunking fist, which for months has appeared to have lacked any force, was back in action, landing blows on the Tories.

After getting his facts wrong the previous week over two Islamic schools - which resulted in an embarrassing apology to the Commons on Monday - Mr Cameron chose to confront Mr Brown on the safer ground of the economy.

With Britain still mired in recession, while major competitor countries are growing again, Mr Cameron had plenty of ammunition. He mocked Mr Brown's boastful claims that he was leading the world out of recession, that Britain had been better prepared for the downturn, as well as his now infamous claim to have abolished "boom and bust".

Such attacks just seem to bounce off Mr Brown, who ignores questions he does not like and ploughs on regardless.

Instead, he seized on the disclosure at the weekend that Zac Goldsmith, the environmentalist and Conservative candidate for Richmond Park, had retained the non-domiciled tax status he inherited from his father, the billionaire Sir James Goldsmith. Being a "non-dom" meant he did not pay tax on offshore income.

The subsequent announcement that Mr Goldsmith had relinquished his non-dom status came too late to save Mr Cameron's blushes at question time. The Downing Street wordsmiths are certainly coming up with better one-liners than the Cameron team.

For Labour, the row over Mr Goldsmith's non-dom status was the perfect political storm - bringing together wealth and privilege, the old Etonian background of Mr Cameron and Mr Goldsmith, and Tory plans to raise the inheritance tax threshold to £1 million.

After all, the proposed Tory cut in inheritance tax is to be funded by a £25,000-a-year tax charge on non-doms - and Mr Cameron is reputed to have more old Etonians around him than any leader since Macmillan.

Mr Brown's parting jibe to the Tory leader was that his tax policies appeared to have been "dreamt up on the playing field of Eton".

The unedifying and rowdy Commons exchanges, with the new Speaker, John Bercow, struggling to keep order, added little to the sum of human knowledge. But they showed how Mr Brown is developing a political strategy to counter the Tories at the next election.

It will concentrate on attacking "Tory Toffs". That line of attack backfired in last year's Crewe and Nantwich by-election, but Mr Brown believes the recession has sharpened the class divide and that message will now resonate with the voters.

He is paving the way for a reprise of Labour's successful "for the many not the few" campaign which swept the Tories out of power in 1997. As he put it today: "Public services for the many versus inheritance tax cuts for the few."

Central to the Labour campaign will be the accusation that despite Mr Cameron's attempts to modernise his party and present a new moderate image, he is still proposing tax cuts for the better off and austerity for the rest.

Mr Brown gave a foretaste of that onslaught, saying that while Mr Cameron might project the "voice of the modern public relations man" he had the "mindset of the 1930s".

He hopes voters will recoil from Tory warnings of spending cuts, preferring Labour's claim that growth is the way to tackle the deficit.

Significantly Mr Brown sidestepped a challenge from Mr Cameron to confirm that Labour would go ahead with its own increase in the inheritance tax threshold from £325,000 to £350,000 next year.

There has been recent speculation that it will be shelved in next week's pre-Budget Report in order to highlight the political divide with the Tories.

The Conservative pledge has already been downgraded as an objective to be achieved by the end of a first Tory government. Given the recession and the need for public spending cuts, some Tories would like it shelved altogether.

But after abandoning his "cast iron" promise to hold a referendum on the Lisbon Treaty, Mr Cameron is reluctant to open himself up to further accusations of a U-turn on a flagship policy.

These are testing times for the Tories. Mr Cameron appears to have lost his surefootedness, with embarrassing stumbles and mistakes while Mr Brown has regained his self-confidence.

A clutch of recent opinion polls suggests the gap is narrowing between Labour and the Tories - raising speculation of a hung parliament. Labour remains in deep trouble, but Mr Brown is nurturing hopes that he could still deny Mr Cameron an overall majority.

A week let alone six months is a long time in politics. After today, there will be more jangling nerves in Tory HQ than in No 10.