Seiken joined The Daily Telegraph in 2013 from PBS.
In an email sent to staff on Thursday, Seiken said: "I'm proud of how the Telegraph has become a digital leader, and I'm gratified that the Telegraph has seen such a large growth in its digital audience. The company has a great future and will continue to thrive. I wish all my colleagues at the Telegraph the very best for the future."
Murdoch MacLennan, Telegraph Media Groups's chief executive, says in the email that Seiken's decision to leave is "regrettable."
"We completely understand Jason's regrettable decision to move onto new opportunities now that he has completed his work here. He has been a much valued colleague, providing a great deal of input into identifying future strategy for the Telegraph Media Group to ensure we remain a world-class and commercially successful media organisation. We wish him well."
Chris Evans will remain as The Daily Telegraph's editor and director of content, where he is responsible for output across all its digital and print platforms. Telegraph Media Group says in its email to staff that Evans' executive editorial team will be "completed" directly after the Easter bank holiday this weekend, wiht the arrival of Matthew Bayley from Sky News as head of content strategy, and Jane Bruton from Grazia as director of lifestyle.
Seiken has made a number of shake-ups to the editorial team since his arrival, which were said to help drive The Telegraph Media Group's "transformation" to digital.
Those changes have led to "tumult" at the newspaper, according to a Financial Times report published last month. The article shed an unfavorable light on Seiken's reign:
There was a problem. Although Seiken was chief content officer, he never tried to run the newsroom. He flew a drone around a seminar of advertisers. He urged the Telegraph to fail more. Meanwhile, reporters wondered what this meant for tomorrow's front page.
The report suggested The Telegraph is suffering an identity crisis, unsure of what its voice is meant to be, or what it is supposed to stand for, particularly with its political coverage. The report continued:
Worse was to follow. Under Seiken, the Telegraph bought the rights to "The Assassination of Margaret Thatcher", a short story by Hilary Mantel. Nothing could antagonise the Telegraph's core readers more: again, MacLennan moved quickly to cover himself. Barely eight months after he had jettisoned [former Daily Telegraph editor Tony] Gallagher, he banished Seiken to an upstairs office at the Telegraph's Victoria headquarters. Reporters went weeks without seeing the supposed editor-in-chief
In February this year, Seiken and his team at Daily Telegraph came under fire after the paper's chief political commentator Peter Oborne resigned, leaving behind a blistering attack on his former employer in a post on the Open Democracy website.In it, Oborne said the newspaper's coverage (or lack of it) on HSBC is a "fraud on readers," accusing The Daily Telegraph of refusing to cover major disparaging stories about the bank because it is a key advertiser.
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