Outgoing BBC director-general Tim Davie has told staff the corporation has to "stand up for our journalism", insisting it will control its own narrative which "will not just be given by our enemies".
Mr Davie quit on Sunday amid a scandal over the editing of a speech by Donald Trump, which has prompted the US president to threaten billion-dollar legal action.
In remarks to BBC staff he said: "We have to be very clear and stand up for our journalism.
"We are a unique and precious organisation, and I see the free press under pressure, I see the weaponisation. I think we've got to fight for our journalism.
"I'm really proud of our work, and the amazing work locally, globally, that we're doing is utterly precious."
He added: "We have made some mistakes that have cost us, but we need to fight for that.
"And I'm fiercely proud of that, and don't let anyone stop you from thinking that we are doing a fantastic job."
Mr Davie also alluded to "enemies" of the corporation, telling staff: "We will thrive and this narrative will not just be given by our enemies: It's our narrative."
A report from Michael Prescott, a former external adviser to the BBC's editorial standards committee, raised concerns that a speech made by Mr Trump before the attack on the US Capitol on 6 January 2021 had been selectively edited by the BBC for a Panorama documentary.
BBC chairman Samir Shah has apologised for an "error of judgment" over the editing.
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US President Donald Trump's lawyers have said the BBC must retract the Panorama documentary by 14 November or face a lawsuit for "no less" than $1 billion.
The legal letter, from Mr Trump's lawyer Alejandro Brito, demands that "false, defamatory, disparaging, and inflammatory statements" made about Mr Trump be retracted immediately.
He plans to issue the proceedings under Florida law.
'Consider what is at stake'
The BBC must "renew its mission for the modern age", Culture Secretary Lisa Nandy has told the House of Commons.
The once-a-decade process of reviewing the broadcaster's charter will begin shortly, with Ms Nandy saying it would ensure a BBC which is "fiercely independent" and "genuinely accountable" to the public it serves.
Ms Nandy warned MPs attacking the broadcaster to "consider just what is at stake".
"There is a fundamental difference between raising serious concerns over editorial failings and members of this House launching a sustained attack on the institution itself, because the BBC is not just a broadcaster, it is a national institution that belongs to us all."
The BBC's charter expires at the end of 2027 and the process of reviewing it is now set to begin with the organisation at the centre of a storm.
Ms Nandy said the charter review process will begin imminently, telling MPs: "Together, we will ensure the BBC is sustainably funded, commands the public's trust and continues to drive growth, good jobs, skills and creativity across every region and nation of the UK.
"In an era in which trust is fraying and truth is contested across our nation, it will ensure the BBC remains fiercely independent and is genuinely accountable to the public it serves."
'Root-and-branch review'
Shadow culture secretary Nigel Huddleston called for the BBC to apologise to Donald Trump for the editing of his speech featured in a Panorama documentary and called for a "root-and-branch review" of the corporation's adherence to impartiality.
Mr Huddleston said: "Does the minister agree that the BBC must provide a fulsome apology to the US President and hopefully avoid legal action? And does she agree that the BBC would do well to apologise to the British public too?
"Does she also agree that we need a root-and-branch review of the BBC adherence to impartiality, particularly as it relates to news and current affairs, and that we need more than apologies and resignations at the top, but clear actions on complaints processing, on governance, on oversight and on compliance to ensure that the BBC sticks to its charter obligations on impartiality and that it rigidly and consistently abides by its own editorial guidelines?"
The Tory frontbencher earlier told MPs: "The BBC is in a sorry mess and, sadly, one of its own making that has resulted in the resignations of the director-general and the CEO of news.
"These recent leadership changes are a response to the growing number of examples of bias in the BBC, one of which has resulted in a potential one billion dollar lawsuit.
"Too many examples have come to light exposing bias at the BBC, particularly as it relates to the news and current affairs output, examples that have often strayed far away from the BBC's own editorial guidelines."
