The report by the Sainsbury Centre for Mental Health found that public spending on mental health services for working-age adults rose by 7 per cent a year in real terms between 1999-2000 and 2005-06, when it topped£4.9bn.
It says spending is likely to rise to£6bn by 2010-11, but that to meet government targets this would need to be£7.5bn.
Staff numbers would need to increase by 38 per cent between 2005-06 and 2010-11 to deliver the NSF goals, including nearly 4,000 more medical staff and 20,000 more qualified nurses.
Sainsbury Centre chief executive Angela Greatley said: 'The mental health NSF was a hugely ambitious 10-year plan. A great deal of extra investment has gone into it. But there remain major gaps, especially in health promotion and primary care, and it now looks unlikely that it will be achieved in full by 2010-11.
'Increasing mental health staffing remains a massive challenge for the NHS and social services. Across all professions and among support staff, recruitment, training and retention need a boost.'
A mixed picture
In primary care, the report says improved access to psychological therapies will require around 11,000 psychological therapists, in addition to the 1,000 new graduate primary care mental health workers and 500 gateway workers announced in the NHS plan of 2000.
For services for people with severe mental illness, it says around 18,000 extra community team staff are needed by 2010-11 if the NSF standards are to be implemented -an increase of around 80 per cent on current numbers.
NHS Confederation policy director Nigel Edwards said the report, Delivering the Government's Mental Health Policies: services, staffing and costs, painted a mixed picture.
'The mental health NSF was one of the first to be published and was very aspirational. But it was never fully costed in terms of what funding would be available over the next few years, and it was before the NHS had its major funding boost.
'Mental health services have managed their budgets quite well, but they are still seen as a soft touch by some managers when financial savings need to be made. The report shows that major progress has been made, but that more staff are urgently needed,' he explained.
Health minister Rosie Winterton said: 'This report provides further evidence of the increased investment in mental health services. We will continue to increase numbers of staff, such as community development workers, and access to a wider range of services such as talking therapies.'
Read the report here