Ever since his activities as a leading anti-apartheid campaigner, which led to a botched attempt by the South African secret service to frame him for robbery in 1975, Peter Hain has rarely been afraid to speak his mind.

It is a trait which has on occasion landed him in trouble with his superiors. In 2003, he was memorably slapped down by the Treasury for daring to suggest that the top rate of income tax should be raised.

Since declaring himself as a candidate for Labour’s deputy, the Northern Ireland Secretary’s habit of courting controversy has continued unabated. In the past few months, he has suggested that city bonuses should be capped; and said, a matter of weeks before the chancellor’s visit with George W Bush in Washington, that the American ‘neo-con mission had failed’.

For Hain, however, it is essential that the forthcoming contest should be about ideas, and not just personalities. In a dig at the campaign tactics of some of his rivals, he describes himself as ‘the only deputy leader candidate who’s actually put forward ideas for renewal and debate. None of the others have put forward any policies or new ideas, and frankly, I think there’s been quite a lot of vacuous stuff around.’

Fresh from securing an historic power-sharing deal between arch sectarian rivals Ian Paisley and Gerry Adams, the Northern Ireland Secretary can perhaps be forgiven for feeling a trifle bullish. He believes his experience on some of the more challenging portfolios in government – including stints at the Foreign Office as a minister for Africa and then Europe, and most recently as Secretary of State in Northern Ireland – has given him the edge over his perhaps less weightier contenders: ‘I don’t think anyone has done as difficult jobs as I have in government in bringing people together, negotiating solutions and finding ways forward.’

But will the Northern Ireland Secretary’s outspokenness lend itself to the role of deputy, a job in which loyalty to the leader and party must often be paramount? ‘The only way you can do this job is to be totally loyal to the leader,’ he assures. ‘But also be prepared to convey messages, in private, in and out of Downing Street, because it’s a two-way process. I think we must have a much more open leadership than we had in recent years, because the longer we’ve been in government it always gets more difficult.’

For Hain, the stakes involved in the contest for Labour’s leader and deputy couldn’t be higher. ‘The way that this leadership and deputy leadership transition happens will determine whether we win the next election,’ he warns. ‘I just think there’s a terrible complacency amongst the other deputy candidates about what we need to do to win. There’s one candidate who wants to go back to the past, there are others who just want more of the same, and I’m the only one who says there’s got to be renewal and reconnection to win.’

This doesn’t mean ‘turning our back on what we’ve done over the last 10 years,’ however. In particular, Labour should be wary of ‘making the Al Gore mistake that allowed Bush to project him as an old democrat, rather than a continuation of the Clinton success.’ Instead, the Northern Ireland Secretary thinks Labour needs to adopt a fresh vision in four main policy areas: ‘We’ve got to make ourselves the leading green force in British politics, we’ve got to tackle inequality, because there’s worrying signs of rising inequality despite all we’ve done. We’ve got to make sure we’re taking forward democratic reform, including completing the Lords reform, and we’ve got to have a progressive international policy.’

The latter is a theme Hain is particularly keen to stress. At the start of the interview he hands us a document outlining a five-point vision of a ‘progressive internationalism’ – reforming the UN; enhancing Britain’s place in Europe; spreading the benefits of globalisation; a renewed effort to tackle climate change; and promoting democracy and human rights around the globe – which aims to ‘heal the breach in the progressive left which the Iraq war has opened up’. The New Statesman recently described Hain as ‘a credible candidate for any one of the foreign-affairs posts under a Gordon Brown premiership,’ and his willingness to highlight this area of his thinking, including in a recent thoughtful speech to the Foreign Policy Centre, suggests he too might also be alive to this possibility.

Meanwhile, the Northern Ireland Secretary has a campaign for deputy leader to win. Will he be taking a leaf from the Hazel Blear’s campaign book by bringing out his own range of Hain hoodies in the near future? He laughs. ‘Emphatically no.’