Never has David Cameron's defence of the government's economic strategy sounded as weak as it did at today's PMQs. Ed Miliband devoted all six of his questions to the subject and came off better each time. Confronted by the worst unemployment figures since 1994, the Prime Minister could only repeat his tired insistence that a change of course would bankrupt Britain.

"You cannot borrow your way out of a debt crisis," he declared but as Miliband reminded him, "to have a credible plan on the deficit, he has to have a credible plan on growth". George Osborne has already been forced to announce £44.4bn of extra borrowing due to lower tax revenues and higher welfare payments.

Cameron hurled criticisms of Labour's economic policy at Miliband, citing Charles Clarke, Alistair Darling and, finally, Digby Jones (which doesn't even qualify as an argument from authority). The Prime Minister, it seems, is taking refuge in consensus. But as any student of the Herbert Hoover administration knows, the received wisdom of the day is often wrong. Cameron should derive no comfort from the endorsement of others. His failure to rebut Miliband's central charge that the government's growth strategy is failing was a sign that he is losing the argument.

Sounding unfortunately bunged up, Miliband still landed several blows on the PM. Reminding him that 400,000 firms were expected to take part in Osborne's National Insurance holiday, he forced a blushing Cameron to admit that just 7,000 had, before neatly seguing into the Liam Fox story. Cameron, he said, was doing everything he could to save the Defence Secretary's job but doing nothing to save the jobs of ordinary men and women."It's one rule if you're in the cabinet, it's another rule for everyone else," he cried.

Asked by Labour MP Pat Glass if a minister should resign if he or she breaks the ministerial code, Cameron replied that it was up to the Prime Minister to decide, confirming that he does not view a breach as grounds for automatic dismissal. He shows every sign of wanting to hold on to Fox but insisted that he would await the conclusion of Gus O'Donnell's investigation. But with the economic situation only likely to worsen, the Defence Secretary's troubles will soon be the least of Cameron's worries.