Department of Health head of public health development George Leahy said that PCT public health professionals must ensure that the joint assessment they are required to complete in partnership with their local authorities is 'focused on outcomes'.
'The needs assessment is the key building block of the commissioning process and is a new duty on local authorities and PCTs,' he said.
Speaking at a Faculty of Public Health conference last week Mr Leahy warned that public health needed to become involved in all parts of the commissioning process.
'We have got to release the money spent on health services into areas which are the main priorities, such as health inequalities,' he added.
Mr Leahy also questioned whether there were sufficient analytical skills available across local government and the NHS to carry out effective assessments and determine the populations' health needs.
Speaking at the same event, Oxford University public health resource unit deputy director Jenny Wright said the public health workforce needed to be much more 'flexible and adaptable'.
'We need to ensure that the workforce is fit for purpose, we need to focus on outcomes and commissioning capability'.
Ms Wright, who is leading the development of a career framework for public health, said there needed to be more emphasis on the 'lower end' of the public health workforce.
'The lower end is a scattered workforce, largely under-regulated, under-developed, and under-utilised but it is poised waiting in line'.
She added that the career framework would provide a 'route map' but public health professionals were 'going to have to relearn commissioning skills in public health'.