ALAN Milburn today marks his return to active politics with a stinging warning that the Government is losing its sense of purpose.

The Darlington MP, who shocked Prime Minister Tony Blair by walking out of the Cabinet in June to spend more time with his family, is calling for next week's Labour Party conference to draw inspiration from Conservative icon Margaret Thatcher and help the Government rediscover its dynamism and direction.

And in a stark message to the trade unions, who he expects to inflict major defeats on the leadership, he says it is "big grow-up time".

"We have to get back into the purpose of being in politics," said Mr Milburn, the former Health Secretary.

"The purpose of being in politics for us on the Left is to make the country a fairer country.

"Somewhere along the way that sense of purpose has got lost and it has desperately got to be restored.

"Mrs Thatcher, whatever people thought about her, had a sense of purpose. Nobody was in any doubt about what she was doing, and in the process she fundamentally altered the political landscape in this country.

"The Blair Government can do the same, but we have to be absolutely consistent in purpose and passionate in belief.

"This sounds slightly old-fashioned, but in an age of cynicism about politics, the public want to know what their politicians really believe in and what the Government's sense of purpose is.

"People are worried about the size of classes and waiting lists, but if you have a grown-up conversation with them, they know you cannot wave a magic wand and put those things right, they are going to take time.

"What they need to know is that there is a clear destination in mind.

"We have got to start that job next week and Tony's speech will be a critical moment."

Mr Milburn has spent the summer recharging his batteries with his family, but is now throwing himself back into the fray. In June, he appeared wearied by the world of politics but yesterday, brimming with new-found vigour, he confirmed that he would be standing in Darlington at the next election.

He has written articles for several heavyweight national newspapers over the weekend.

This morning, he will make his first appearance on Radio 4's Today programme since his dramatic resignation.

Mr Milburn was Mr Blair's closest Cabinet ally, and commentators have spent the summer speculating about how he will help the Prime Minister rebuild his badly- bruised image.

Yesterday, there were stories that the Darlington MP would mastermind Mr Blair's bid for a third election victory. But Mr Milburn, in his exclusive interview with The Northern Echo, said: "No, I am not writing the manifesto but of course I will want to have a say about where we are and where we go as a government and as a Labour Party."

After Labour's traumatic summer, next week's conference will be the most important since 1997, with Mr Milburn's policy of foundation hospitals being one of the most controversial topics.

Mr Milburn said: "I think it is likely on several issues the leadership will be defeated, but the policy will still happen because it is right.

"Unfortunately, a few delegates want to inflict defeats. That's pretty hopeless. They have got to understand their history a bit more. As soon as a party starts to look disunited it has problems. So it's a big grow-up time, really."

* Read the full interview with Mr Milburn in The Northern Echo tomorrow.