As one of the country's most powerful watchdogs, Ofcom is used to issuing rebukes when broadcasting and telecom companies fail to meet its exacting standards.
But now the industry regulator has had to give itself a public slap on the wrist after breaking its own rules on premium-rate phone lines.
Ofcom has been at the forefront of efforts to ban the expensive tariffs, which consumer groups have condemned as a rip-off.
But it has been forced to apologise after asking applicants for a senior job within the organisation to dial an 0870 number.
Calls to such numbers cost about 8p a minute, almost three times the 3p charged by BT for calls to ordinary landlines, with a portion of the money going to the organisation that runs the line. The rate is higher if the call is made from a mobile, with many firms charging several times as much.
Ofcom recently urged public bodies to scrap premium-rate lines and use normal 'geographical' numbers instead. But when it tried to fill the senior post of Principal Broadcasting Adviser, applicants were invited to have an informal chat about the job by telephoning an 0870 line.
Henry Ejdelbaum, of accountancy partnership AIMS, said: "These numbers take advantage of small businesses and the public. Why should someone receive commission for taking a phone call?'
When The Mail on Sunday asked Ofcom about the cost of a call to the job application line, we were referred to headhunters Drax. We put the same question to a Drax executive, who said: "I thought 0870 numbers were free."
Ofcomhas admitted its mistake and said it would take more care with its recruitment ads in future.
A spokesman said: "The job advert was placed by Drax, one of Ofcom's external recruitment agencies. We have agreed that all future external Ofcom recruitment adverts will include a geographic telephone number. We apologise to applicants for any inconvenience."
The job advert had appeared online and in several newspapers and industry journals.
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