The hire comes as the organisation prepares to communicate the conclusions of its telecoms review and increases regulation of internet telephony.
Hirst, who joins in August, will develop telecoms and technology PR strategy.
The regulator's audience includes telecoms firms, consumer groups, government, media and City analysts.
'The day of Ofcom telling companies what they should do is over,' said Hirst. 'Now it is more of a discussion.' He reports to director of comms Matt Peacock, who described the body as a 'deregulating regulator' with a 'priority to reduce the regulatory burden on companies'.
Hirst will attempt to keep stakeholders informed about Ofcom's stance on issues such as telephone numbering, silent calls from telemarketing firms and premium rate numbers.
Other issues include the future of fixed line and mobile telecoms and the regulation of BT.