Leading article: The hard work starts here

There is no rest for newly elected leaders. At the weekend, Ed Miliband scraped through in an emotionally draining contest to lead the Labour Party. But straightaway he faces two immense challenges. He must decide the composition of his Shadow Cabinet and also the strategy that he will adopt to oppose the Coalition Government over the coming years. The two challenges are inextricably connected.

On the first, much depends on the intentions of the new leader's elder brother, David, whom he narrowly defeated for the leadership. The senior Miliband made a gracious speech yesterday at the Labour conference and a passionate plea for party unity. But he has yet to decide whether he will make himself available to serve in his brother's Shadow Cabinet.

The departure of Mr Miliband, one of the most experienced senior Labour politicians, would weaken the party's front bench. But more than that, it would send off a potentially damaging signal. The contest between the brothers was inflated (somewhat inaccurately) into a battle between the left and right of the Labour Party. If Mr Miliband were to step down, it would be widely interpreted as more evidence of leftward lurch by Labour.

Mr Miliband is also faced with the tricky question of how to utilise the talents of the Shadow Education Secretary, Ed Balls. Mr Balls ran a feisty campaign for the leadership and he has shown himself to be adept at opposition politics. The obvious position for him would be Shadow Chancellor. Yet Mr Balls's rejection, in recent weeks, of the pre-election Labour plan to halve the deficit by the end of this Parliament is potentially dangerous.

Mr Balls is right to criticise the pace of the deficit reduction being imposed by the Coalition. And the Conservatives did exaggerate the threat of Greek-style meltdown. But the argument about the need to maintain confidence in Britain's sovereign credit is not entirely spurious. Alistair Darling's March Budget did seem to help to calm investors' nerves. When the Eurozone sovereign debt crisis reached a critical phase in April, Britain was regarded as a safe haven. Without Mr Darling's commitment to bring down the deficit, Britain could indeed have found itself in crisis. Tearing up what the former Chancellor rightly yesterday called the "balanced" approach to deficit reduction would be a gamble.

Labour's new leader needs to choose very carefully both on personnel and strategy in the next few days. A mistake now could do grave damage to the Opposition's chances of a relatively swift return to power.