As an employer, OrangeGenie has a legal responsibility towards its freelance contractors, customers and the public. We could be held legally liable if a freelance contractor or a member of the public is injured as a result of negligence or breach of duty by one of our freelance contractors.

Liability insurance is designed to pay any compensation and legal costs that occur if an employer or freelance contractor is found to be at fault.  
Your Agency/Client will insist you are covered by liability insurance before you will be allowed to enter the client's premises.
You are automatically covered for:

Employers' liability insurance enables businesses to meet the costs of compensation and legal fees for employees who are injured or made ill at work through the fault of the employer.  Employees injured due to an employer's negligence can seek compensation even if the business goes into liquidation or receivership.

This type of insurance covers any awards of damages given to a member of the public because of an injury or damage to their property caused by you or your business. It also covers any related legal fees, costs and expenses.

And you may need to consider:

This policy protects a professional freelance contractor against compensation sought by a client if you have made mistakes or are found to have been negligent.
Professional indemnity insurance will also cover any legal costs..
If you are in the business of selling your knowledge or skills, you may want to consider taking out professional indemnity insurance.  Most professionals carry professional indemnity cover.