"We expect the BBC to defend its independence and report impartially, robustly and fearlessly on all issues relating to Brexit and not succumb to any pressure to skew its coverage one way or the other," the letter, initiated by a group of House of Commons members led by Labour's Pat McFadden and obtained by The Guardian, said.
The cross-part group of over 80 members of parliament, which included Liberal Democrat leader Tim Farron and former leader Nick Clegg, former Conservative Education Secretary Nicky Morgan and former Culture Secretary Ed Vaizey, asked BBC Director General Tony Hall to resist any political interference just around a week after a rival group of lawmakers accused the public broadcaster of biased reporting on Brexit.
UK Prime Minister Theresa May triggered article 50 of the Lisbon Treaty on Wednesday, thus starting the process of leaving the European Union.