Director-general Tim Davie launched the ten-point plan two years ago.
But a review of its output by the Campaign for Common Sense suggests its drama and news is failing to uphold those standards.
A Campaign for Common Sense spokesperson said: “This research reveals that, rather than upholding those high standards of impartiality, parts of the BBC continue to peddle a steady diet of woke bias both through the plotlines of popular dramas but also in some of its news coverage.
“The Impartiality Plan, unveiled in the wake of a BBC scandal over trust, was supposed to mark a turning point for the corporation.
“Instead this research reveals the same old woke world view is still very much in operation.
“Two years ago, the BBC set itself very high standards to help restore viewers’ trust. It has singularly failed to meet those standards.”
The BBC News website has featured 55 stories linking Britain to the transatlantic slave trade — more than one a week in 2023.
But the BBC hit back: “Cherry-picking a handful of examples is not a true representation of BBC content.
“We are proud that our output seeks to represent all audiences and a range of stories and perspectives.
“Across the entirety of our services there will, of course, be occasions when people disagree with or want to challenge what they have watched or heard and we have well-publicised routes for them to do that.”