Brazilian President Luiz Inácio Lula da Silva’s campaign has requested the disqualification of right-wing challenger Flávio Bolsonaro in the lead up to the final round of the presidential election on Sunday over alleged interference by social media company Meta.

In a petition filed to the country’s top electoral court on Wednesday, the leftist incumbent president accused Meta, the tech giant behind Whatsapp, Instagram and Facebook, of limiting its content to boost Bolsonaro’s campaign.

In response, Bolsonaro filed a petition seeking to disqualify Lula over what he said was the mass dissemination of government posts on WhatsApp.

The company has denied the campaigns have been treated unequally.

It comes after UN experts said on Wednesday that they were concerned about reports of discrepancies in the ability of each campaign to reach voters on Meta’s platforms.

A report led by the UN’s special rapporteur on freedom of expression said Meta must ensure a level playing field online during the election.

It cited incidents including “temporary interruptions of one candidate’s campaign account; differences in audience engagement, user feeds, view counts and reach; restrictions on that campaign’s Instagram posts”.

“Information, including from Meta employees, suggests that accounts linked to one side of the presidential race were disproportionately curtailed,” it read.

Meta has denied taking action to favour one side of the election and has said it would comply with an order from a Brazilian court to treat Bolsonaro and Lula equally.

Lula’s campaign had previously filed a complaint alleging that accounts and content related to Bolsonaro were boosted.

Users also reported that Meta’s artificial intelligence tools were not generating images related to Lula.