This is a question I was asked yesterday by a business owner who has just taken on an employee.
The answer is no, not as a rule. Employers liability insurance is almost always offered as part of a combined liability policy, along with public and products liability, or as a section in a package insurance policy.
The best way to decide how best to get employers liability cover is to speak to an insurance broker, who specialises in business and commercial insurance. They will be able to advise you as to the best and most cost-effective way to arrange employers liability insurance for your company. This will depend on your particular situation and the type of work you are involved in. They will usually get you several business insurance quotes from different insurance companies and then recommend the most appropriate one for your business.