A contract of employment is a legal agreement between the employer and the employee. It contains terms, either express or implied, which cannot lawfully be changed or varied by the employer without further agreement from the employee (either individually or through the trade union). In some cases the contract may contain an express term apparently permitting the employer to make changes from time to time. Even where such a clause exists, these changes would need to be reasonable and introduced appropriately.
Additionally, where changes are made to your contract, employers must give you written notification of the change within 4 weeks. However, that does not change the fact that an unauthorised, one-sided variation is a breach of the contract of employment. The fact that the employer gives notice to vary the contract does not make the variation lawful if you (or the trade union) do not agree to it.
The options open to you when faced with such a situation range from refusing to accept the variation to resigning and claiming 'constructive dismissal'. Well before taking such a drastic step as resigning you should get legal advice. Refusal to accept the change may result in the employer dismissing you. Although you might be able to claim unfair dismissal and breach of contract, the employer might defend the case on the basis of 'some other substantial reason' as a statutory fair reason for dismissal.
If your employer is seeking to vary your contract and you are unsure whether to accept the changes, or what to demand in return for agreeing to the change, seek advice from your union rep, or a legal advisor.
