A political leader who witnessed a black guest being “interrogated” about where she “really came from” at a Buckingham Palace reception has called for a “culture change” within the monarchy.

Mandu Reid, leader of the Women’s Equality Party, was stood next to Sistah Space founder Ngozi Fulani at the event hosted by the Queen Consort on Tuesday when she overheard a longstanding palace aide challenge the British-born advocate by saying “Where do your people come from?”

She said the encounter left them “pretty stunned”, branding the experience a reflection of the wider situation in British society and very dangerous and disturbing.

Speaking of the experience of the Duchess of Sussex who said an unnamed royal made racist remarks about her unborn son, Ms Reid said: “It does fit into the accounts Meghan has given and the experience she’s had.”

She added: “It’s not that I didn’t believe (Meghan) at all but having experienced that first hand, it was so casual which tells you how normalised it is.

“There was nothing furtive about it…and that is always a sign that these behaviours, these patterns, are baked into the fabric of how things go day to day.”

Ms Fulani revealed how “Lady SH” – Lady Susan Hussey – the late Queen’s former lady in waiting who has now resigned amid the serious race row – persistently asked where she was from and challenged her when she said she was British.

Ms Reid, the first person of colour to lead a national political party in British history, told PA she was stood in a group of three which included Ms Fulani and another black woman.

“We really felt ‘Oh, OK, we’re being treated almost like trespassers in this place’,” she said.

“We’re not being treated as if we belong, we’re not being embraced as if we are British.”

She described the exchange as “grim” and like an “interrogation”, adding: “She was really persistent. She didn’t take Ngozi’s answers at face value.”

Ms Reid said the Palace workforce did not reflect the diversity of the British population and that it was potentially a “hostile environment”.

“It’s potentially a hostile environment for people from certain backgrounds. And so it’s no good just saying ‘We’re going to get some more bums on seats’. You’ve got to change the culture within the institution,” she said.

She added: “This isn’t just about the royal family and Buckingham Palace. There are threads of this through many different aspects of British society at the moment. It’s really, really dangerous.

“When you zoom out and look at the bigger picture. It’s very very disturbing.”

Ms Fulani and Ms Reid were among more than 300 guests at the Queen Consort’s first major solo event in her new role, where she was championing the work of those helping survivors of domestic abuse.

Ms Reid added: “I think what’s really awful about it is you got to remember the context, right?

“The reception was put on to celebrate and honour people who have been working and work day in day out to end violence against women and girls.

“And it was also there to elevate the importance of that subject yet, for at least three of us who were there we had an encounter which undermines the whole purpose of the event, undermines us people who were guests and there to be celebrated and supported for the work we do.”

She said the remarks had left Ms Fulani, who she knows well and who is usually outspoken and confident, deflated.

“To be honest, both of us felt very deflated in the immediate aftermath of that conversation. We were pretty stunned. And it kind of stole our joy,” she added.