Who'd have thought Iain Duncan Smith would become Jeremy Corbyn's latest (unofficial) cheerleader?

Rather than make Labour irrelevant, the Work and Pensions Secretary's resignation may offer the beginning of a new surge

While few will be quick to offer Jeremy Corbyn any credit for the fact that the Tory party is currently ripping himself apart it is important to remember that it was the Labour leader that set the ball rolling (PA)

Jeremy Corbyn’s passionate response to the Budget on Wednesday was peppered with many of the usual Labour slogans. Though perhaps predictable that Labour would hammer home the message of cuts being a political choice and not an economic necessity, few would have been prepared to bet on Iain Duncan Smith joining in with the chant by the weekend. In his resignation letter, Duncan Smith noted that the cuts to the disabled seemed "distinctly political rather than in the national interest". And while having Iain Duncan Smith on board would really test the "broad church" mentality of the Labour party it is great to see that Jeremy’s vision of inclusion can even win over the most despised of Tories.

While few will be quick to offer Jeremy Corbyn any credit for the fact that the Tory party is currently ripping itself apart it is important to remember that it was the Labour leader that set the ball rolling. With his strong response and determined focus, Jeremy Corbyn ensured that the £4.4 billion cut to personal independence payment was centre of the agenda. In the days that followed the Budget it was his rallying call against the Government that picked up traction and dominated discussion. It was perhaps the strongest line of his response: "I simply ask the Chancellor this: If he can finance the giveaways he has put in his Budget to different sectors, why can't he fund the need for dignity for disabled people in this country?" It is a question that the former Work and Pensions Secretary has clearly had trouble coming to terms with.

In just one speech Jeremy Corbyn has turned up the heat on Tory divisions and has blown the Cabinet apart. And let’s not forget that it’s only four days since the Budget; it certainly feels as though this saga is not over yet. In exposing Osborne’s economic failure Jeremy Corbyn has stoked division within the Tory party without even having to explicitly do so. Nicky Morgan, the Education Secretary, couldn’t even bring herself to defend the Budget on Question Time, instead arguing that the cuts to disability benefits were mere ‘suggestions’. And now the man who fired the starting pistol on the destruction of the welfare state thinks Osborne has gone too far. The civil war within the Tory party is raging and Corbyn deserves some credit in forcing its advancement.

Tactically this is also an important boost for those loyal to the Labour leader. The Blairites had been ramping up the rhetoric on fiscal responsibility in the week heading into the Budget with Rachael Reeves and Dan Jarvis each offering an alternative message. It seemed that they had been gambling on failure, wishing that Jeremy would be knocked out by the Chancellor’s rhetoric so that the ground could be laid for an eventual coup. But things could not look better for the leadership right now. The polls are showing sustained public dissatisfaction with the Tories and this latest debacle will only boost that. Labour has taken a lead in one of these polls for the first time since the election and Corbyn’s stance has split the cabinet. Rather than Duncan Smith’s resignation making Labour irrelevant, it may have just offered the beginning of a new surge.