It is understood that Jones, who joined the Hutchison Whampoa-owned company two years ago, does not have another job to go to. According to sources, his departure comes during a restructure of the UK operation.
Jones, a former Orange sales director, was drafted in by chief executive Bob Fuller in May 2003 to reverse the poor performance of the company, which had struggled to make an impact following its launch that March.
The pair moved 3's £40m ad account from TBWA\London to WCRS and then embarked on an expensive strategy of massively undercutting rivals on voice calls to sell its 3G phones. 3's extensive TV advertising included obscure brand ads developed by Jones and his brand team.
Last month 3, which is the UK's fastest-growing mobile operator, having signed up 3.2m customers in less than three years, unveiled plans to become a mobile media company. It is seeking a media agency to sell advertising on its network.
3 declined to comment on Jones' departure.