The actions of the BBC’s board have shown the broadcaster’s enemies that a “leak and launch” tactic can succeed in destabilising the corporation, according to a board member who resigned after a row over alleged bias.

Shumeet Banerji, a tech industry investor, quit the board on Friday after stating he felt he had not been properly consulted on the events that led up to the sudden departure of director general Tim Davie and the head of BBC News, Deborah Turness.

In remarks in his resignation letter that pile further pressure on the BBC’s chair, Samir Shah, Banerji suggests Turness was effectively forced out, validating the tactics of the corporation’s detractors.

He said he missed one board meeting, before stating that at a second, he had been “surprised to hear on the call that Turness had already been told that she did not have the confidence of a majority of the board”.

“I was not invited to any meeting where a matter of such importance was to be discussed,” his letter states, adding Shah had not allowed “reasoned discussions” to take place.

His remarks appear to contradict claims from Shah. Appearing before a committee of MPs on Monday, Shah pushed back on Banerji’s claims of being excluded. He said he had a 26-minute call with Banerji over the weekend of the two resignations.

Banerji appears to be disputing that, stating they spoke because he requested the call. He said he was releasing his resignation letter to BBC News, which first reported it, to inform misconceptions which may have arisen from Shah’s appearance for committee members and viewers.

The resignations of Davie and Turness followed the publication of a memo written by Michael Prescott, a PR executive and former independent external adviser to the BBC’s editorial guidelines and standards committee.

Prescott claimed there were “systemic problems” with the BBC’s coverage of issues including Donald Trump, Gaza and trans rights. A fellow adviser who served alongside him disagreed with his account this week.

Banerji warned that the board’s reaction to Prescott’s memo, and the coverage it received after being “predictably leaked” to the Daily Telegraph, meant the corporation had effectively given encouragement to its enemies.

“The evaluation of the performance of executives is a board matter, but not in the white heat of a press excoriation,” he wrote. “This is what has happened here. The lesson for detractors of the BBC is leak and launch.”

Banerji’s letter adds that, as a result of Turness’s treatment by the board, it is “inconceivable to me that Tim Davie did not see this as a direct assault on himself, as the editor-in-chief and CEO”.

Davie has said that while the crisis was part of his decision to resign, it was not the sole reason.

At the time of Banerji’s resignation, a BBC spokesperson said: “Shumeet Banerji today notified the BBC board of his resignation. Mr Banerji’s term on the board as a non-executive director was due to end at the end of December and we thank him for his service.

“The search for a replacement is already well under way and we will update further in due course.”