According to sources, the former British Gas marketer will leave the business to work on a series of personal charitable projects.
It leaves Mark Evans, director of brand portfolio and partnerships, as the most senior remaining marketer at the insurer. Evans will operate as interim chief marketing officer. However, it is not known if Direct Line is looking for a permanent replacement for Vlemmiks.
The group, which owns brands such as Churchill, Green Flag and Privilege, rebranded from RBS Insurance earlier this year, with RBS compelled to sell the assets by the end of 2014 under the terms of its bail-out by the UK government in 2008.
Vlemmiks took up the role as chief marketing officer in February from his position with British Gas, to head up the insurer's newly formed centralised marketing structure, ahead of the sale.
Direct Line Group was unavailable for comment.
UPDATE: It is understood Vlemmiks will remain contracted to Direct Line Group until December, but will no longer work at the business on a day-to-day basis.
Follow Matthew Chapman at @mattchapmanUK