Constructive Dismissal is where an employer has committed a serious breach of contract, entitling the employee to resign in response to the employer’s conduct. The employee is entitled to treat him or herself as having been “dismissed”, and the employer’s conduct is often referred to as a “repudiatory breach”. 

It can be difficult for a non-legal person to understand why your resignation should be referred to as a “dismissal”. All you need to know is that in legal terms, the actions of your employer (the “constructive part”), has led to your resignation (the “dismissal” part). The law then treats the resignation as a form of unfair dismissal by your employer or to quote the full correct terminology, “constructive unfair dismissal“.

It is not enough to show merely that your employer has behaved unreasonably. There must be a fundamental breach of either an express contractual term, or the implied term of “trust and confidence”. Furthermore, you must have resigned because of the actual breach- not for some other reason. You should also make it clear at the time that you regard yourself as having been “constructively dismissed”.