Subject to a basic minimum floor of rights, such as the right to be paid at least the National Minimum Wage, and to minimum statutory holiday, the terms of the employment contract – and any changes to those terms – are a matter for the employer and employee to agree.
However, there is very significant inequality of bargaining power in the employment relationship for most workers. This is one of the main reasons why collective bargaining by a recognised union is so important. It helps to redress the imbalance and achieve better contract terms than individual employees could hope to achieve acting alone.
Employers should consult staff in order to obtain agreement to changes to the contract, for example introducing a new shift pattern. They should also provide enough advance warning to enable staff to prepare for any change. Imposing changes without consulting properly or without providing enough notice of the proposed changes is likely to be a breach of the implied contractual duties of mutual trust and confidence and good faith.
Sometimes it is possible to resist planned contract changes on the basis that they impact negatively on groups of workers with protected characteristics under the Equality Act 2010 in a way that cannot be justified by the employer. This is known as indirect discrimination.
For example, changes to shift patterns can impact negatively on women with childcare responsibilities. Changes of this kind would need to be justified by the employer in order to be lawful, for example by pointing to a good business case for making the changes.
The fact that proposed changes impact disproportionately on groups of workers will not necessarily mean that the employer will not make them, but it may help to persuade them of the need to meet workers half-way.
In practice, it can be very difficult to prevent changes to contractual benefits or their withdrawal altogether. However, you will have a better chance if you act together through a recognised union.
Where those affected by the proposed changes include disabled workers, the employer has a statutory duty to make reasonable adjustments to prevent the changes impacting unfavourably on disabled workers, when compared with to their impact on non-disabled colleagues.