Can my employer prevent me from working for a competitor after I leave?

A restriction in the contract of employment preventing you from working for a competitor after leaving your current employment is called a 'restrictive covenant' or 'restraint of trade' clause.

It is not unusual to see an express term in the contract of employment limiting employment with a competitor, or setting up on your own in competition, for a limited period and within a limited area.

Such 'restraint of trade' clauses will only be upheld in law if they can be shown to be reasonable, to be protecting legitimate business interests and to be in the public interest.