http://www.direct.gov.uk/en/Employment/ ... G_10027549
Civil law and picketing
You can lawfully join a picket line as long as the picketing is:
* connected to a trade dispute which you are involved in
* carried out at or near your own workplace
* carried out peacefully
If any of the above doesn't apply, an employer may be able to sue you or your union for damages under civil law. If the employer threatens to take action against you, you should ask a solicitor for advice. Your union will have one that can act on your behalf.
Secondary picketing
If you're a worker on a picket line in dispute with your employer, you can peacefully try to persuade workers who aren't affected to support you. For example, you may try to persuade lorry drivers from a different employer not to deliver supplies. This also applies to trade union representatives lawfully present on a picket line.
However, it's unlawful to picket other companies' premises whose workers are not in dispute. For example, if you are on strike you should not go to your employer's customers' premises to encourage their workers not to handle your employers goods. Picketing of this kind is called 'secondary picketing'.
Picketing activities shouldn't interfere with workers not connected with a dispute who use the same entrance as those on strike. For example, if you work in an office block shared by different firms, you shouldn't try to picket workers from the other firms
