The leader of Southall Black Sisters has appeared in court alongside two friends charged with assaulting a woman in King’s Cross Underground station.

Selma Taha, 52, the executive director of the advocacy group for black and minority ethnic women, has been accused of assault over the incident but claims that she and her two co-defendants were the victims of a “violent racist attack”.

She appeared at Highbury Corner Magistrates’ Court on Thursday alongside Divina Riggon, 40, and Danae Thomas, 52.

All three are accused of assault by beating in the central London Underground station on September 29 last year.

In a statement issued last week before the hearing, Taha said the complainant in the case against her had accepted a caution for racially aggravated conduct under the Public Order Act and no further action was taken.

Dozens of people gathered outside the court on Thursday with placards that read “drop the racist charges”, “stop police dishonesty”, and “get up speak up for your rights”.

Riggon and Thomas were originally also charged with harassment under the Public Order Act.

But during Thursday’s hearing, Thomas’s charge was raised to the more serious offence of racially aggravated harassment contrary to the same Act, which could be tried at a crown court.

In her statement before the hearing, Taha added the racially aggravated harassment allegations are for her friend’s “conduct towards a white British Transport police officer”.

She said: “It would not be appropriate for me to make further public comment given this development, save to confirm that we will be fighting the charges, and that we regard these charges as criminalising the right of black people, and in particular black women, to call out racist abuse and resist racist violence.

“I also want to express my gratitude for the support shown by so many of you to date, and to ask that you continue your support in the weeks and months to come.”

A judicial review may also be launched by the defendants, who are all from Warwick Road, Kensington, their defence barrister Harry Charalambous told the court.

The case was adjourned until April 26 at the same court because of the change to the charge and potential judicial review.

Postponing the hearing Neil Taylor, chair of the magistrates’ bench, said “there is an expectation” that magistrates take pleas in the first occasion and that “justice delayed is justice denied”.

He said: “The expectation is (by April 26) there will be clarity in respect of whether a judicial review application has been lodged or not, we also expect on that occasion that defendants could be fully prepared on the changes in charge.”

All three defendants spoke only to confirm their names, dates of birth and addresses.

Southall Black Sisters’ website states “we provide a specialist service to some of society’s most marginalised victims of abuse”.