Balls's speech made way for a new agenda that is profoundly exciting.{C}

Ever noticed how shutting one door can open another? This week Labour's staunchest champion of growing our way out of the deficit acknowledged that he could well be making cuts in 2015. The left, personified by Owen Jones and Len McCluskey, were up in arms. They think we've lost the possibility of being radical. I say we've opened it up.

The modern left frequently makes one mistake. They assume that the most significant means government has of transforming lives is through taxing and spending, traditionally known as the "demand" side of the economy. They have left the supply side - the rules that govern the price of labour and capital - to the right.

But what if, at a time of pressure to reduce government spending, the left could develop an agenda for the supply side of the economy that delivered meaningful change?

It's not surprising we're sceptical. Because the right have dominated such policy in the past, such an agenda is associated with smashing unions to decrease the cost of labour, deregulating capital to enrich the fortunate or privatising at the expense of quality.

But supply side policy doesn't have to be regressive. It's just a tool that's been used in the wrong way. Most recently, Ed Miliband has been talking about a number of supply side policies that are courageous, imaginative and proudly consistent with the values of the left.

The most high profile example is his attack on certain energy and transport companies. We know that these markets are sown up, so increasing competition and regulation will deliver a fairer result. The living wage is another example. Government contracts that build in apprenticeships and local investment is another. The High Pay Commission's work on wage transparency and shareholder representation on boards is another. Cutting down on corporate tax havens as Miliband just outlined is another. Breaking up the banks takes this one step further.

Although it needs sexier branding, these supply side policies are all part of what Miliband calls "responsible capitalism". It's why Blue Labour is interesting.

These policies have three big advantages. First, they don't cost anything. Second, they make people's lives better. Third, they are much closer to where the public is at. I appreciate the arguments made by Owen Jones, but I don't think he has appreciated the scale of anger there is about a perceived waste of public money by Labour in the good times.

As someone who remembers what it was like to not have enough chairs in their classroom, I'm never going to apologise for investing in schools, and you'll never hear me say that government spending isn't essential and necessary. But waste on IT contracts, PFI and middle managers? I'm happy to apologise for some of that.

And as Ed Balls said this week, a true Keynesian is sometimes a hawk. If you genuinely believe we should be running a programme of increased spending now, then you have to acknowledge that we should have spent less when the economy was booming. The idea that Keynesians believe in high spending throughout the cycle misses the point completely.

So let's not get confused - Labour is still saying that we should cut less fast and less deep now, but with the OBR estimating we'll be 18 per cent poorer as a result of the recession, the state will be smaller once we're out of this mess. And that means a progressive supply side agenda.

If we do that, then Ball's speech wasn't a sign of giving up and following the Tories slowly back to the middle ground. It was a necessary part of gaining credibility with the public to make way for a new agenda that is profoundly exciting. Interestingly, it's one that Miliband is leading, not the shadow chancellor. The left shouldn't abandon ship, it should get on board.