Gay rights campaigner Peter Tatchell has been called racist and 'transphobic' by a student union officer ahead of a debate the pair were both invited to speak at.

Fran Cowling, the lesbian, gay, bisexual and transgender (LGBT) representative for the National Union of Students, has refused to appear at Canterbury Christ Church University tomorrow, unless Mr Tatchell does not attend.

Ms Cowling stated in emails to event organisers that she could not share the stage with Mr Tatchell, because he signed an open letter in the Observer last year supporting free speech and against no-platforming, the practice by some universities to ban speakers because of their views.

Accused: Peter Tatchell has been called racist and 'transphobic' by NUS officer Fran Cowling, who refuses to attend a planned debate if the veteran gay rights campaigner also attends

According to the NUS officer, the letter supports inciting violence against transgender people. Cowling has also made an allegation against Mr Tatchell of racism or using racist language.

Speaking to the Observer, the political activist, who will soon celebrate 50 years of campaigning for gay equality, called the incident another example of 'a witch-hunting, accusatory atmosphere' at university campuses today.

Mr Tatchell's stance on free speech was questioned earlier this month when he surprisingly came out in support of a Christian bakery company that refused to sell a cake with a gay rights slogan.

Ashers Bakery in Belfast were found to have broken anti-discrimination laws when they declined an order for a cake with the slogan ‘support gay marriage’.

Mr Tatchell said: ‘Much as I wish to defend the gay community, I also want to defend freedom of conscience, expression and religion.’

As a result of the court ruling against the bakery, far right agitators could force Muslim printers to publish cartoons of the Prophet Mohammed, or Jewish printers to reproduce Holocaust denial material, he added.

‘Will gay bakers have to accept orders for cakes with homophobic slurs?’ he asked.

‘The law against political discrimination was meant to protect people with differing political views, not to force others to further political views to which they conscientiously object.’

LGBT officer Fran Cowling refuses to appear with Peter Tatchell at a planned debate in Canterbury

Australian-born Tatchell, 64, first sprang to fame as a left-wing Labour candidate, when he lost the party’s once safe Bermondsey seat in 1983.

During the 1990s, he campaigned for LGBT rights through the direct action group he co-founded, OutRage!

The group grabbed the headlines by outing establishment figures it claimed were homophobic in public and homosexual in private.

In 1999 and 2001, he attempted a citizen's arrest of Zimbabwean President Robert Mugabe for his anti-gay stance, the latter resulting in a vicious beating by Mugabe's thugs.

Six years later in 2007, Mr Tatchell was among dozens of people assaulted by Russians shouting 'death to homosexuals' against protesters demanding the right to hold a gay pride parade in Moscow.

The veteran campaigner says both these incidents have left him with lasting brain injuries.

Unafraid to put across his point of view, Mr Tatchell said he would share the stage with Ms Cowling at tomorrow's event, despite their difference of opinion.

He said: 'I'm prepared to share a platform with people I profoundly disagree with, precisely in order to challenge and expose them.'

The NUS said Tatchell had not been 'no-platformed' by the entire union and that Ms Cowling's decision whether to appear is her own.