At last, some real protection has been introduced for zero hour contract workers.
In force today (11 January 2016), The Exclusivity Terms in Zero Hour Contracts (Redress) Regulations 2015 provide that:-
any dismissal of a zero hour contract employee is automatically unfair, if the principal reason is that s/he breached a contractual clause prohibiting him/her from working for another employerno qualifying period is required to bring such an unfair dismissal claim; and,it is also unlawful to submit a zero hour worker (note: worker not employee) to detriments if they work for another employer in breach of a clause prohibiting them from doing so.
Comment
You may be interested to know that in October 2015 the Department for Business, Innovation and Skills published guidance on zero hours contracts. The guidance includes what they are, best practice, appropriate use and how these contracts affect employment rights.