Labour campaign chief Alan Milburn has said the government's drive towards choice in the public sector is a response to a "tidal wave" of demands from voters.

In an interview with the Guardian ahead of this weekend's party spring conference, the Cabinet minister says it is right that Labour introduces the principle along "egalitarian" lines according to an ability to pay.

The former health secretary is seen as the leading champion of extending market forces into health and education, but has faced criticism that the idea goes against Labour's traditions of equity and a public service ethos.

However he said responding to the people's needs is the only way of ensuring the long term future of publicly funded schools and hospitals.

"Now the public debate is this: people exercise choice in every other branch of their life; increasingly they recognise that the private sector offers choice; that is a real problem for the public sector," he said.

"I worry about that a lot. If the private sector offers choice and the public sector does not, it ceases to command confidence. It's also an egalitarian argument.

"[Demand for] choice is out there; if we try to avoid it, there will be a tidal wave. It's inevitable. It's coming. What we want a system [of choice] based on need, not the size of your wallet."

Milburn claimed Labour has won the argument in the last two elections over whether public services should receive more cash.

"The debate has moved on so far that even the Tories have recognised that money has gone in," he said.

But he argued that the party must now do the same on the new debate over how best to reform them or risk losing increasing numbers to the private sphere.

"Parents want to do the best for their children, that is right, but a lot of them would like to do that in the state system," the minister insisted.