Employers proposing 100 or more redundancies must now start consultation at least 45 days before any dismissals can take effect. This has been reduced from 90 days.
Acas' new guidance aims to help employers understand their legal obligations and sets out principles and behaviours to help employers manage collective redundancies more effectively.
Acas Chair Ed Sweeney said: "This new guidance draws on our knowledge, expertise and experience in helping to resolve the thousands of workplace disputes every year.
"In 2011/12, 11% of Acas' collective conciliation cases related to redundancies and of the 925,000 calls to our helpline, around 20% were seeking information on redundancy-related situations.
"This guide will help employers and employees understand the recent changes and the new laws around collective redundancies with top tips on how to handle them."
Acas advises that for organisations to manage collective redundancies well, they need:
- Good working relationships with employees, unions and employee representatives
- Agreed procedures for handling redundancies
- An organisational culture that recognises the emotional as well as economic impact of change; and a plan for restructuring and looking to the future