A BBC manager has turned down a promotion after discovering she was offered £12,000 less than a man in the same job, she has claimed, as she shames the corporation in writing over its ongoing gender pay gap row.

Karen Martin, a radio producer and news editor, told colleagues by email that she could not accept the role of deputy editor in the BBC radio newsroom after learning that a man, appointed at the same time, had been offered a higher wage.

In an email to current and future colleagues at the corporation, she said she had turned down the job on principle after discussing the matter with her young daughters and concluding she must “stand up for what is right”.

The BBC responded with an email from Gavin Allen, head of BBC news output, who argued: “I accept that we have not always got things right in the past on pay but I believe this is not one of those cases.”

The public dispute reignites a BBC row about equal pay, which saw dozens of high profile female broadcasters protest in support of their colleague Carrie Gracie.

Gracie, who resigned as China Editor, eventually received around £280,000 in back pay from the BBC, together with a public apology, after winning her gender pay battle.

Tony Hall, director-general, has pledged to close the gender pay gap credit: PA

In March, it was confirmed that the corporation is being investigated by the Equality and Human Rights Commission over suspected pay discrimination against women.

“Despite being awarded the same job, on the same day, after the same board, during the same recruitment process, BBC News asked me to accept a considerably lower salary than my male counterpart. A lot less,” Martin told BBC radio news staff by email, according to the Guardian.

“I’ve been assured our roles and responsibilities are the same. I’ve also been told my appointment was ‘very well deserved’. It’s just that I’m worth £12,000 less.

“Over the past four months I have asked BBC News to think again. And they’ve inched their offer up by addressing historical ‘under payments’. Now the gap is nearer to £7,000.

“But for me it has never been about the actual salary. It has been about equal pay.”

The other deputy editor is reported to be Roger Sawyer, said by the BBC to have worked “at or above this level for several years” to justify his higher salary.

Martin added that her two daughter, aged seven and 13, had advised her: “‘You always tell us to stand up for what is right. If it means less pocket money or not going on holiday, we don’t mind. What matters to us is that when we grow up we want to be paid the same as a man for the same job.’

Carrie Gracie, who received an apology and pay out from the BBC credit: PA

“And just like that, my decision was made.”

A source confirmed that the dispute involved different salaries within the pay band of £60,000 to £100,000.

In an email to staff, Allen said: “I regret that Karen has decided not to take this opportunity. I think it important to explain what has happened in this instance.

“As you know, we don’t have fixed rates for jobs. Instead we have pay ranges as agreed with our unions.

“In setting pay for this particular role we have taken the view that Roger and Karen would be doing roles of equal weight as Deputy Editors of the Radio Newsroom.

“We also took into account the fact that Roger has worked at or above this level for several years whereas Karen was offered this role as a promotion, with a significant pay increase.

“We think most people would understand that these factors would result in some difference between their individual pay.

“I want to reassure you that we have followed a proper process for this appointment as well as the BBC’s principles on fair pay. We cannot give out individual salary figures but they are both considerable and entirely appropriate.”