Yes zero hours contract are legal. They are contracts that are provided to casual and sessional workers. They are ideal for an employer wishing to have a flexible workforce to meet fluctuating work demands. Zero hours contracts are used extensively in the hospitality industry and social care sector. They operate on a mutual no obligation relationship; the employer has no obligation to offer work and the worker has no obligation to accept the work. For the employer it is advantageous to have a bank of casual staff to call upon when increased demand arises and to be sure that someone will be available to do that work.
Zero hours contracts only command pro rata holidays in terms of employment rights and it is important to keep records of hours completed to calculate holiday pay. Holidays can then be paid quarterly or, if appropriate, on a rolled up basis carefully following the rules for rolled up holiday pay. Workers with zero hours contract should be used on an ad hoc basis only so that additional employment rights can not be pursued in an employment tribunal.