Several Conservative MPs say they will not take part in unconscious bias training provided by the House of Commons.
The training aims to tackle prejudices people are unaware they hold, on issues like race and gender.
Writing in the Mail this week, Ben Bradley called it "Orwellian" and "totally nonsensical".
Speaking on Thursday, Commons leader Jacob Rees-Mogg said it was for MPs to decide if they wanted to participate.
He said: "Finally, the House has made unconscious bias training available, and if people want to do it, that is a matter for them."
The House of Commons said the training was being done under a pilot scheme after it was requested by MPs. Attendance is voluntary.
It said the two-hour online session raises awareness of unconscious bias and explores practical ways of tackling it.
Mr Bradley, Conservative MP for Mansfield, said the training represented the "second phase of our re-education" after MPs attended sessions about valuing people in the workplace.
He added: "It seems totally nonsensical to me that, in my role as a representative of a community that has typically felt left behind and voiceless for many years, I should be advised that there are certain words I shouldn't use; certain issues that I should avoid; certain sensibilities that I should not offend.
"How am I to raise the true feelings of an electorate that broadly feels like it's being preached at by a metropolitan elite who neither understand nor care about them, if I have to walk on eggshells and dance around the problem?"
Several of his colleagues tweeted their agreement, including David Warburton, the MP for Somerton and Frome, who said he would "go no further down this rabbit hole".
The Times has reported that up to 40 Conservative MPs could refuse the sessions.
The trade union Prospect, which represents some public sector workers, said Parliament "should publicly and strongly reject the arguments put forward by MPs on unconscious bias".
Its deputy general secretary, Garry Graham, added: "All MPs should undertake the training that their own black and Asian employees see as a crucial step in improving their day to day working lives.
"What kind of message does it send to the country if a couple of hours of training is too high a price to pay to demonstrate that tackling racism and unconscious bias is a priority?"
The House of Commons has provided unconscious bias training for its staff since 2016.
Asked about the sessions for MPs, it said: "We are committed to creating an inclusive workplace and, following requests from MPs, we have made unconscious bias training available to them on a small pilot basis.
"These are not mandatory, and the pilot is expected to be completed in the next few weeks."
Labour introduced training after its leader, Sir Keir Starmer, was criticised for calling the Black Lives Matter protests "a moment".