Gordon Brown has put the brakes on public sector demands for bumper pay rises.

A tough-talking chancellor warned there will be no "blank cheque" for pay claims from NHS staff and other public sector workers.

"Just as sustained economic growth demands responsibility in setting private sector pay, so a sustained commitment to better public services demands responsibility in setting public sector pay - and discipline will be our watchword," he said on Thursday.

He echoed the words of health secretary, Alan Milburn, who told nurses on Wednesday not to expect big pay rises.

Downing Street has also warned that there will have to be wage restraint following the Budget.

Brown, at a conference on public services, repeated his demand that increases in productivity and modernised working practices will have to come with any pay deals.

He set out four overriding principles that will guide the government's decisions: money will go direct to the frontline, there will be clear plans and targets, organisations must be flexible to change and pledge to put the consumer first.

To counter union unrest over the increasing role of the private sector, he also reaffirmed the commitment to public services but warned ministers will not be held to ransom over pay settlements.

"Those of us who believe passionately in public services have a special responsibility to ensure their effectiveness, to understand that there can be no blank cheques, and that the days of something for nothing are over in the public services," he said.

Brown argued that achieving Labour's goal of creating world-class public services would not happen where the organisation was not up to standard. He cautioned against "resistance to necessary change".

"We can only deliver world-class public services if strings are attached and we change, update and modernise to ensure that public services can best serve the public," he said.