Don Brash says he's "dumbfounded" after being "uninvited" from a speaking event at Massey University.

The former National Party leader, who formed treaty lobby group Hobson's Pledge, was due to speak at Massey's Manawatu campus on Wednesday, as part of a series of politics talks.

But Dr Brash told Newshub he was told by the event organiser he should not be on the campus, due to security concerns.

"I got the invitation two and a half months ago. This morning I was advised I should not be on campus due to security concerns," he said.

"I was asked to talk about my time in Parliament, and why I should be banned is entirely unclear," he told Newshub.

Dr Brash is a controversial figure, recently complaining about the use of Te Reo greetings on RNZ and throwing his support behind legal action against Auckland Council over its refusal to allow two far-right Canadian speakers access to a council-owned venue.

The planned event sparked protest from some students.

One published a letter on Facebook addressed to the Vice Chancellor Jan Thomas.

The letter raises concerns about providing "a platform for separatist and supremacist hate speech".

"Their type of "Free Speech" does not come Free of Consequences," the letter concludes.

Professor Thomas says the event booking was cancelled due to security concerns.

"Mr Brash's leadership of Hobson’s Pledge and views he and its supporters espoused in relation to Māori wards on councils was clearly of concern to many staff, particularly Māori staff," Professor Thomas said.

"It is clear there is heightened sensitivity and passion at this time, following the protests both against and in support of [Lauren] Southern and [Stefan] Molyneux's right to be heard. Our ultimate responsibility is for the safety and wellbeing of students, staff and members of the public on our campuses and under those circumstances cancelling the booking is the right thing to do."

ACT Party leader David Seymour says Professor Thomas should resign for the "cowardly barring" of Dr Brash.

"I have long feared that American-style anti-intellectual, violent intolerance would come here," Mr Seymour said.

"It has appeared at Massey this week and the university has completely failed the test."

The Free Speech Coalition, which was formed in July with the aim of challenging Auckland Council over the cancellation of the far-right speaking event, says "thugs" have been "emboldened" by the Council's cancellation.

"If we allow the 'heckler's veto' to shut down contentious speech at a university, a place that should be a bastion of free expression, what hope can we have for free speech anywhere else?" spokesperson David Cumin said.

Newshub.