WhatsApp is once again raising concerns about how it is being used to disseminate fake news. This time, the problems with the Facebook-owned messaging platform are centred around the upcoming presidential election run-off in Brazil.

Facebook has discussed its own efforts into clamping down on the spread of misinformation, but its messaging service is being bombarded with false claims and conspiracy theories. And left-wing candidate Fernando Haddad is accusing businessmen supporting his right-wing opponent, Jair Bolsonaro, of paying to flood voters with misleading propaganda, according to Reuters, a claim which is denied by Bolsonaro.

With over 120m users in Brazil, WhatsApp is one of the top ways that Brazilians stay in touch with each other. This fact is part of the reason why Bolsonaro has been so successful in his presidential campaign despite having little access to public campaign funding or TV advertising. The seven-term congressman has been able to use a large presence on social media to help him win 46 per cent of the election’s first round vote earlier this month.

However, the false rumours and manipulated content shared on WhatsApp could have violated electoral laws.

Brazilian newspaper Folha de S.Paulo reported that Bolsonaro supporters had paid digital marketing firms millions of reais to spread thousands of attack ads about Haddad. The left-wing candidate has claimed to have witnesses that heard his rival encouraging business leaders to fund these efforts.

In addition to this, the way that marketing companies obtained the mobile phone numbers of WhatsApp users may have violated Brazil’s data privacy laws.

On the possible breaches, WhatsApp has said it is taking the allegations seriously and is taking legal action to prevent companies from sending out bulk messages – including sending out cease-and-desist letters to the companies involved.

Brazil isn’t the first nation to struggle with the spread of fake news on WhatsApp. This year has seen several stories out of India about the platform’s alleged role in a number of lynchings carried out on the basis of false information.