"You can’t tell me any additional measures that you’ve put in place," Yvette Cooper tells the PM.
People involved in the Oxford University trial have stressed there's no cause for concern.
The protest has been organised to draw attention to the impact of Covid-19 on indigenous people in Brazil.
More than 260,000 people tested positive for the virus worldwide on Saturday.
The virus he has sloughed off has killed more than 65,000 Brazilians. And even after he tested positive, Bolsonaro treated it as no big deal.
The far-right leader has spent months downplaying the severity of Covid-19 even as cases surge in his country.
The US, Brazil and UK have so far seen the highest number of Covid-19 victims.
As the world's death toll closes in on half a million, cases in Brazil are still accelerating and infections in India may not peak until November.
Health officials reported more than 900 deaths in Brazil on Friday.