Jonathan Halvorson has left General Motors (GM) just eight months after joining, a spokeswoman has confirmed, with no replacement yet named.

Ad Age reports that it is unclear what prompted his departure from the automotive behemoth, where he reported to general director of global marketing services Megan Stooke and was tasked with coming up with a “more accountable and innovative” media strategy.

Before moving to GM, Halvorson was managing director for Starcom Mediavest Group, GM’s media agency until 2012, where he looked after the Mondelez International account.

GM is one of the world’s biggest advertisers. According to Ad Age data, in 2013 the auto manufacturer was the fifth biggest-spending brand owner, investing $3.35bn in measured media.

Halvorson was a judge at this year’s Festival of Media LatAm Awards in Miami. He spoke to M&M Global about the quality of work emerging from the region – watch below.