Companies may eventually be forced to provide a separate email system for employees sending personal messages, according to the Data Protection Registrar.
The warning came after Oftel announced last week that companies should provide an unmonitored telephone line for personal calls.
Assistant data protection registrar Phil Jones said that if email became more popular, a similar move would follow for text messages. Jones said the telephone was currently a more necessary form of communication, so employees needed confidential access to it. But he added that the increasing popularity of email could change this.
"We are not saying that employees should have to have private email yet, but if email eventually replaces voice as the main way of communicating then a similar ruling should apply," he said.
Dai Davis, IT advisor at lawyers Nabarro Nathanson, said the Oftel ruling should be extended to include email.
"If you're allowing employees to make unmonitored phone calls then, logically, you should also provide the facility to make unmonitored emails," he said.
He added that there should be some specific legislation to guarantee privacy in the workplace to both employees and employers.
Oftel's announcement requires companies that routinely record telephone conversations to provide staff with a separate, unmonitored telephone line for personal use.
Companies that fail to comply could be in breach of Article 8 of the European Convention on Human Rights, which covers peoples' right to privacy.
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