ADLO director John Roberts said councils have to revise their budgets year on year in line with the annual settlement from the government. They therefore cannot make long-term staffing commitments.
'A strict regime will be restricted by unions and public sector managers,' said Mr Roberts. 'It could lead to over-manning.
'The insecurity in the public sector has been caused by competition and contractualisation. If they end CCT the insecurity will change.'
Shadow employment minister Peter Hain revealed Labour's proposals in Monday's Guardian newspaper. He held up two private company agreements as an example.
Mr Hain said: '[Job-security agreements] could be negotiated in return for increased flexibility, leaving the pay bill effectively neutral.'