Picketing occurs when a group of people gathers outside a workplace to try and persuade others, such as non-strikers, substitute workers or suppliers, to take some form of industrial action.
It should be distinguished from demonstrations, which take place where people wish to put a case across to others, but are not trying to induce them to break their contracts. Picketing is an indirect form of industrial action that is protected by the law in the same way as industrial action in general, i.e. by the system of trade union immunities, regulated under the Trade Union and Labour Relations (Consolidation) Act 1992.
For those taking part to retain immunity from legal proceedings, the picketing must be in contemplation or furtherance of a trade dispute and consist only of peacefully obtaining or communicating information, or peacefully persuading any person to work or abstain from working. It must take place at or near the picket's place of work and must not involve any other breach of the civil law, such as trespass or nuisance. In addition the union must appoint a union official or other member of the union who is familiar with the statutory Code of Practice: Picketing to supervise the picket (the picket supervisor).
The union or picket supervisor must take reasonable steps to tell the police:
- the picket supervisor’s name
- where the picketing will be taking place and
how to contact the picket supervisor.
The union must also provide the picket supervisor with a letter stating that the picketing is approved by the union and the supervisor must, if asked by the employer (or an individual acting on behalf of the employer), show the letter to the employer (or individual), as soon as is reasonably practicable.
While picketing takes place, the supervisor must be present or be readily contactable by the union and the police and be able to attend at short notice. The supervisor will also have to wear something that readily identifies them as being the picket supervisor.
If employees have more than one place of work, they can picket the premises from which they work, or from where their work is administered. The same applies to workers for whom it is impracticable to picket at their place of work because of its location. People who have lost their jobs in connection with the dispute may picket at their former place of work as long as they are unemployed (and the dispute remains). Union officials other than the picket supervisor, can picket at or near the place of work of any member they represent.
Where picketing takes place, employees not directly involved in the industrial action may refuse to cross picket lines. Such employees can normally be regarded as being on strike and treated accordingly. Occasionally however, employees may be willing to cross picket lines but are reluctant to do so for fear of their safety. In such circumstances, the authority should try and ensure that the employee is given every protection in crossing the picket line, or where practicable, is given the opportunity to work at another establishment. If the authority considers the employee has made every effort to cross the picket line but was unable to do so, then the authority may decide not to treat their absence as industrial action.
Picketing will often involve secondary action in that pickets may try and persuade employees who are not in dispute with their own employer to break their contract (e.g. lorry drivers delivering supplies). This is the only circumstance where secondary action is protected by the law. However, the pickets themselves must be in dispute with their own employer.
Mass picketing is likely to fall outside the immunities because it is unlikely to be conducted peacefully and is likely to involve employees who are not picketing at their place of work. In addition, trade unions that organise picketing may be in breach of torts that are not covered by the statutory immunities. For instance, in News Group Newspapers v SOGAT 82 (No 2)  IRLR 337 QBD the High Court held that although a union is not vicariously liable for the tortious act of nuisance simply because it organises a picket, it could be liable if it does not take any action to prevent the tortious act re-occurring.
The ' Code of Practice: Picketing' contains advice on:
- the lawful purposes of picketing
- how to seek redress
- picketing and the criminal law
- the role of the police
- limiting the numbers of the pickets (the code suggests a maximum of 6)
- the right to cross picket lines
The code is not legally enforceable but the courts, where they consider them relevant to any proceedings, may take its provisions into account.
The usual remedy sought by employers subject to picketing is an interim injunction, effectively ending the industrial action. Due to the Human Rights Act 1998, the courts are required to consider the implications of Article 10, the right to freedom of expression, and Article 11, the right to freedom of assembly, on the law of picketing. The courts must consider whether granting an injunction is an interference with the free exercise of these rights, and whether such interference can be justified.