A person who contravenes section 21(1) is guilty of an offence and liable—
on summary conviction, to imprisonment for a term not exceeding six months or a fine not exceeding the statutory maximum, or both;
on conviction on indictment, to imprisonment for a term not exceeding two years or a fine, or both.
In proceedings for an offence under this section it is a defence for the accused to show—
that he believed on reasonable grounds that the content of the communication was prepared, or approved for the purposes of section 21 in accordance with subsection (2A) of that section, by an authorised person; or
that he took all reasonable precautions and exercised all due diligence to avoid committing the offence.