The NHS constitution will force the government to invest in services and act as a protective 'firewall' against budget squeezes, advisers have predicted.

But Constitutional Advisory Forum members are also recommending the draft document is beefed up by replacing the word "strive" with phrases referring to what patients and staff can expect from the health service.

The forum is today handing health secretary Alan Johnson a document containing recommended changes to the constitution.

Clear statement

Forum member Will Hutton, who is the Work Foundation executive vice chair, said: "If we get it right it will be clear what the NHS stands for many years ahead and any government will be obliged to finance it.

"It puts a firewall around the NHS for the next three to four years against savage squeezes in public expenditure."

The forum also wants the wording to allay fears that the constitution will impose centrally driven values.