Bill Clinton took to the stage with his old friend Tony Blair today to reinforce the Prime Minister's message that Labour will have to remain "an agent of change" if it is to stay in power, able to implement policies that affect the lives of real people.

In a relaxed, almost rambling, speech to the Labour conference the day after Mr Blair's impassioned valedictory address, Mr Clinton spoke of the need to balance global leadership with what he termed "home improvement".

He delivered a firm warning, based on his own experience since leaving office, that the "other guys" cannot be trusted to keep the good bits if you let them take power.

Mr Clinton's address - the kind of easy anecdotal speech that Mr Blair himself could soon be delivering if he follows his old ally onto the international speaking circuit - came after Labour had turned its gaze outwards with a Q&A on the fight against poverty.

The star turn in that debate was Bob Geldof, the Live Aid founder, who provided the most controversial moment of the day when he gave his backing to the anti-aids programme espoused by Mr Clinton's successor, President Bush.

The Bush Administration launched the $15 billion President's Emergency Plan for Aids Relief (Pepar) in 2003 but it has been criticised because around one-third of the funds go to faith-based groups that smack of Christian fundamentalism.

Sir Bob told delegates that Aids had stabilised in Africa - partly because of condom distribution, but added: "Pepar, which is Bush's almost personal response to the Global Fund, is a highly effective Aids combatant mechanism. It works. It's uncomfortable for people to speak these unspoken truths but a lot of that stuff is working."

He continued: "In general in rural Africa women have no power. They also cannot refuse sexual favours.

"What this if you like fundamental Christian agenda - and believe me I'm an atheist so I'm not going along with that - what it has done is I've seen marked in chalk on these rural huts - safe sex, fidelity. It's giving women a weapon they can use."

With his familiar southern cadences flooding through the hall in a converted Manchester railway station, Mr Clinton spent much of his speech praising Labour's record under Mr Blair and "the brilliant economic leadership" of Gordon Brown.

It was no accident, he said, that one of the world's most progressive governments had also delivered economic success, no accident that Britain had managed to boost employment while still delivering on its obligations under the Kyoto Protocol - while America still maintained that reducing carbon emissions would hit economic growth.

Indeed, he said, the fact that the media focused more on Labour's internal divisions than on its policy achievements was a sort of backhanded compliment - too many people in Britain blithely assumed that economic stability was guaranteed, that the good times would last for ever.

"I saw how you reacted to Tony Blair's speech yesterday. I want you reach back across the years and remember how hard it was for those young people ten years ago to develop the ideas appropriate to that time, then how hard it was for those to stay on the cutting-edge of change all of this time, and how important it is that you still be seen as the agents of change because none of us have an option to be anything else.

"When I read stories about politics in the UK or in America and they seem to be more calculated to spur resentment and insecurity rather than enlightenment, and more focused on internal conflict rather than what the impacts of policies are on real people in their real lives, I realise that in a funny way that is a backhanded compliment to you.

"If we were in the great depression nobody would be writing that. If there were no effective security policies and you felt scared every moment of every day no one would be writing that,. If people were at each other's throats no one would be writing that. That too is a testament to your success.

"But one of the things that a party can do is to remind its less partisan, less politically-inclined neighbours that underneath all the crash and smash and splash there are real policies that have a real impact on real people's lives."

To loud applause from delegates, Mr Clinton added: "I think your biggest problem right now is that people take your achievements and your ideas for the future, for granted.

"I think that you have produced prosperity with social progress for so long that it's easy for people to believe that it's just part of the landscape. That either its going to happen anyway or if you get a set of new faces in the driver's seat surely they wouldn't change what's working.

"I have been there."

Mr Clinton said that under his leadership, the United States had been on its way to becoming debt-free as a country for the first time since 1837, a situation that would have given it room to invest in the most disadvantaged.

Under Mr Bush, the US Government had been borrowing trillions of dollars, borrowing even from countries such as Mexico with much lower per-capita incomes.

"We borrow money from the Mexicans to pay for Bill Clinton's tax cut," he said. "I say that to show that it can change quickly."

Mr Clinton ended his speech with a lengthy aside on another lesson learnt since leaving the White House, in his new role as a campaigner against HIV/Aids.

He told delegates about a word he learnt in southern Africa, the concept of Ubuntu, an "almost mystical" Bantu word which summed up the reality of an interdependent world.

"Literally, in English, it means: 'I am because you are'," he said.

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