His departure is understood to be over the failure of management to provide a launch date for the title. Associated Newspapers is also planning an evening freesheet.
Orlov is the former ad director on the Evening Standard, but left the newspaper in November 2002 after the departure of the managing director, Sally de la Bedoyere.
He joined the launch team at Express Newspapers six months later to build a classified and display sales force for the free title. He poached Karen Newton, a senior advertising executive, from his old employers at Associated.
The question over when the Express' London paper will launch has yet to be resolved. The freesheet was originally planned for March 2003 and then for the summer of that year, but there is still no sign of the title.
Last year, the Northern & Shell chairman, Richard Desmond, reaffirmed plans for the paper. But London's Mayor, Ken Livingstone, is likely to invite rival news-paper groups to pitch against the Express for transport distribution of an evening freesheet.
Express Newspapers and Orlov were unavailable for comment as Campaign went to press.
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