Journalist Carrie Gracie has resigned as the BBC's China editor, saying the corporation was facing "a crisis of trust" and accusing it of "breaking equality law".
The BBC News Channel told viewers of Gracie's resignation, which she claimed wasprompted by unequal pay within the corporation.
Gracie had accused the corporation of a "secretive and illegal pay culture" after it was revealed two-thirds of its stars earning more than NZ$280, 000 were male.
The letter says: "My name is Carrie Gracie and I have been a BBC journalist for three decades. With great regret, I have left my post as China Editor to speak out publicly on a crisis of trust at the BBC.
"The BBC belongs to you, the licence fee payer. I believe you have a right to know that it is breaking equality law and resisting pressure for a fair and transparent pay structure.
"In thirty years at the BBC, I have never sought to make myself the story and never publicly criticised the organisation I love.
"I am not asking for more money. I believe I am very well paid already - especially as someone working for a publicly funded organisation. I simply want the BBC to abide by the law and value men and women equally."
A BBC spokesman said: "Fairness in pay is vital. A significant number of organisations have now published their gender pay figures showing that we are performing considerably better than many and are well below the national average.
"Alongside that, we have already conducted an independent judge-led audit of pay for rank and file staff which showed 'no systemic discrimination against women'.
"A separate report for on-air staff will be published in the not too distant future."
Gracie, who is a China specialist and fluent in Mandarin, said she left her post as China editor last week.
She said she would return to the TV newsroom "where I expect to be paid equally".
A fed-up Ms Gracie condemned the BBC for the way it was reviewing the pay of female staff in the letter which was leaked to BuzzFeed News.
She said: "Many have since sought pay equality through internal negotiation but managers still deny there is a problem.
"This bunker mentality is likely to end in a disastrous legal defeat for the BBC and an exodus of female talent at every level."