Steve Richards: They may be leaders in waiting, but neither Balls nor Miliband is ready for the top job

Two cabinet ministers touted as possible future leaders move to the centre of the stage this week. Today, the Schools Secretary Ed Balls launches his ten-year Children's Plan, so ambitious in range and timescale that today's eight- year-olds will be adults by the time it is fully implemented. Tomorrow, David Miliband, the Foreign Secretary, will appear before the Commons foreign affairs committee on the eve of the signing of the EU reform treaty. In its ceremonial order, the signing will fail to convey the storms that lie ahead. One of Miliband's tasks is to calm the tempest.

Most ministers in this government attract little attention for the sound reason that insecure administrators are not especially interesting. Balls and Miliband are partial exceptions. Balls made waves last month when he announced that diplomas would be introduced alongside A-levels and that the education leaving age would be raised to 18 both potentially highly significant reforms. In order to outline his thoughts on Europe, Miliband dared to head for Bruges, a location that Margaret Thatcher made legendary. More widely, he appears often on the Today programme to respond to various international crises. Yesterday, he was navigating around the politics of the Balkan region in a peak-time slot.

But the focus on the duo is more intense because of the wider context. For some in the Labour Party, one or the other represents the future as the next leader. In the strange frenzy of recent weeks, there has been some speculation that a leadership contest might even come before the next election. In such weird circumstances, scrutiny of the duo becomes greater still.

There is logic to the interest. Miliband worked for Tony Blair from 1994. Balls toiled for Brown from an even earlier point. They therefore fit neatly into a depressingly familiar narrative. Some close to Blair hope that Miliband will rise to the very top. Several influential Brownites keep their fingers crossed that Balls will succeed the Prime Minister.

Thankfully, the reality is not quite as neat as that. Miliband is not an ultra-Blairite. I would not be surprised if he recognised the limitations of the simplistic focus on "choice" in public services and the lack of any local accountability in relation to policy innovations such as city academies. He was not a great fan of the schools White Paper published two years ago, which was regarded by Blairites as an almost biblical text. Even so, Miliband is influenced enough by his old boss to adopt many of his mannerisms the jacket off, the neatly ironed shirt, the self-deprecating jokes. When Miliband appears before committees of MPs, he has in mind, perhaps sub-consciously, Blair's masterful performances as Prime Minister in front of the liaison committee.

In policy terms, Balls had more influence on Brown than Miliband did on Blair. Brown was a politician, not an economist. As the Shadow Chancellor from 1992, he knew Labour had to change its approach to the economy while finding the money to invest in public services and to redistribute to low earners. Balls, a trained economist, provided the detailed route map.

Balls is also a victim of his closeness to Brown. He is the Blairites' favourite enemy, and perceived as the key conspirator against their hero. In Anthony Seldon's recent biography of Blair, the name of Balls comes up more often than just about any other individual. He is always the figure behind the arras with a dagger in his hand. Miliband is less burdened by enemies. On the whole, he has kept away from scheming, although the speculation over the summer that he might succeed Blair has had its impact. He flexes his muscles more these days. The Foreign Office minister, Lord Malloch Brown, came to learn that Miliband was his boss after making the occasional indiscretion. Miliband also fought back when he wrongly suspected No 10 of briefing against him over his Bruges speech. Having risen with ease, he seeks to learn belatedly the art of political street-fighting close to the top.

In policy-making terms, Balls thrives. Business leaders still miss him as a Treasury minister. Now he has a wide remit in areas that touch some of Brown's favourite themes education and poverty. Some of those close to Miliband suspect that Balls's brief is too meandering and imprecise. More specifically, a former cabinet minister tells me that Ball's plans for offering A-levels and diplomas simultaneously will cause chaos. We shall see. For now it can be said that, unlike most ministers, Balls is instigating a range of tangible reforms in ways that command broad support.

From the loftier perspective of the Foreign Office, Miliband's scope for policy-making is more limited. He also struggles to outline a broader vision. He made an attempt to do so in his speech at Labour's conference, but without success. After the speech, the BBC could not decide whether to get over-excited because Miliband had rejected Blair's foreign policy, or because he had endorsed Blair's approach. I seem to remember that the BBC resolved the problem by simply getting over-excited.

Miliband struggles to define his politics through foreign affairs, although he has made thoughtful speeches and statements on specific, thorny areas including Europe and Iran. He was more successful in linking ideas and policies when he was Environment Secretary. In that newly fashionable brief, he brought the issue to life with one or two electrifying speeches and by ensuring that a climate change Bill was part of the legislative programme (although David Cameron's support for such a move played its part). Miliband also made much of a vague brief as Communities minister, seeking new ways of defining the relationship between the citizen and the state. Even so, Miliband has moved from job to job so frequently sometimes reluctantly that he has yet to be fully tested as a policy-maker.

Perhaps Miliband would have been wiser to stay at the Department for Environment, Food and Rural Affairs and use his soaring political capital in the summer to beef up the job. Conversely, Balls wisely decided long ago not to press to be Brown's first Chancellor. He needs to make his mark as a policy-maker in a separate Whitehall department or the damaging attempts to label him as a Mandelson-type schemer will hit home fatally.

Both have still to find fully their public political voices. Milband's delivery can be over-rehearsed. He is, though, engaging and conversational key qualities in the media age. Recently, Balls has looked more relaxed on TV but he can still appear as if he is trying to relax, which is a different matter. The brief comparison suggests neither Miliband nor Balls is ready to be a leader, let alone Prime Minister, one of the many reasons why I do not believe there will be a leadership contest before the next election. As far as they are seen as leaders in waiting, it is in their interests to wait a lot longer.

s.richards@independent.co.uk