ED MILIBAND, leader of Britain’s opposition Labour Party, is not a natural when it comes to talking economics. He famously forgot to mention the country's budget deficit—the dominant economic issue in British politics—in his September address to Labour’s party conference. But in a speech on December 11th he appeared self-assured and well-briefed as he set out, in broad terms, what public spending would look like under a Labour government.

On the economy, Mr Miliband faces an uphill battle. The governing Conservative party has a huge lead on economic management: 16 percentage points according to a recent poll. Labour, on the other hand, is perceived as spendthrift. Mr Miliband sought to put this right by setting out his plans to reduce government borrowing, which will be £91 billion ($143 billion), or 5% of GDP, this financial year. The speech made clear that deficit reduction would be a priority for a Labour government. “There is no path to growth and prosperity for working people which does not tackle the deficit,” Mr Miliband hawkishly declared.

Despite the tough language there is a large gap between the two main parties on fiscal policy—the biggest since 1992, according to Paul Johnson of the Institute for Fiscal Studies, a think-tank. That is partly due to the extremity of the Conservatives' plans, which aim produce a budget surplus of £23 billion by the 2019-20 financial year. This is a tougher goal than George Osborne, Britain’s chancellor of the exchequer, has set himself before, both in terms of the measure of the deficit used and the plan to produce a surplus. By contrast, Mr Miliband promises to balance only current expenditure, which excludes investment spending, with receipts. On today’s plans, that would allow the government to produce a deficit of up to £25 billion by the end of the next parliament. The difference between the two plans—£48 billion—may amount to as much as 3.3% of GDP in 2019-20.

As a result, Mr Miliband has to tread an awkward path between convincing the public that he is serious about achieving his deficit target and championing the fact that it is looser than the Conservatives'. The speech managed that tricky job well. Mr Miliband emphasised the necessity of cuts every year until 2020, but slammed the Tories' plans to shrink the state to just 35% of GDP—a level last seen before the second world war. Mr Miliband declined to say how big he thinks the state should be, but his target points to around 38% of GDP, plus whatever spending he is prepared to finance with new taxes.

This plan is certainly more achievable than Mr Osborne’s, but the Tories say it would not bring down the national debt fast enough. The Treasury reckons balancing the current budget would bring debt down from 81% of GDP in 2014-15 to around 60% of GDP by 2035-36, compared to around 35% of GDP under Mr Osborne’s plan. In truth, either would be sustainable, but the lower the debt burden, the easier it is to respond to future shocks, such as another financial crisis.

The other aspect of Labour’s strategy is to link the debate on the deficit to a topic with which they are more comfortable: low wages. During the second half of this parliament Labour has argued that stagnant real wages have caused a “cost of living crisis”. Now, they emphasise the adverse effects of this trend on the public finances; income tax receipts have disappointed, preventing the deficit from coming down as fast as the government had hoped.

This is the right criticism, but Labour is short on solutions. Mr Miliband wants to raise the minimum wage, and talks vaguely about education and infrastructure producing fatter pay packets. But there is no substantive plan to address low productivity growth, which is the fundamental cause of the twin problems Labour has identified. In truth, it is not something that government policy can easily solve—at least, not in the short-term.