George Alagiah said the decision to step down was not his
BBC newsreader George Alagiah has resigned as a patron of the Fairtrade Foundation over concerns of a potential conflict of interest.
Writing in the charity's magazine, he said "senior colleagues at the BBC" had decided that the unpaid position was "no longer compatible" with his job.
There were concerns that the role "could undermine my impartiality" when reporting on Fairtrade food, he added.
A spokesperson for the charity said: "We are extremely disappointed."
The spokesperson added that no "formal explanation" had been given about the decision.
In his letter, which was published in the summer edition of the charity's magazine, Alagiah said it was with "great regret that I have to tell you that this will be the last time I write as your Patron".
The presenter noted that the "decision is not mine".
"In the many years that I have been your patron there has not been a single complaint (that I am aware of) to the BBC, so you can imagine how taken aback I was by the decision," he added.
Later this month, Alagiah will be seen presenting a BBC Two series called The Future Of Food, but the BBC said this was only partly responsible for its decision.
In a statement, the corporation said: "This is not a judgement on fair trade but is about ensuring the impartiality of the BBC.
"George is a news journalist and this is a charity which takes a position on food and trade and promotes those views to the public.
"We fully understand that the decision is a very disappointing one for the Fairtrade Foundation and for George, but the BBC has a duty to protect its reputation for impartiality."
Alagiah has presented the BBC's Six O'clock News by himself since Natasha Kaplinsky's departure to Five in 2007.
The Fairtrade Foundation is an independent non-profit organisation. It works towards making sure there is greater equity and fairness in international trade.
Alagiah's wife, Frances Robathan, is head of fundraising at the charity.
Meanwhile, director of BBC Vision Jana Bennet has defended BBC One controller Jay Hunt following newspaper allegations of a potential conflict of interest.
Speaking to The Guardian, Ms Bennet said that although Ms Hunt's husband ran a media training business and the controller was its company secretary, she had "no involvement in the day-to-day running of the business, nor any involvement in any contracts that the business has with the BBC".
She added Ms Hunt was a "hugely talented leader" and should be judged on her professional record.