The party of Brazil’s outgoing president Jair Bolsonaro has challenged the outcome of the runoff election he narrowly lost last month, calling for the cancellation of ballots from electronic voting machines with alleged malfunctions.

The far-right populist was defeated on October 31 by his leftist rival and former national leader Luiz Inácio Lula da Silva, who picked up 50.9 per cent of votes in the tightest presidential election in the history of the South American country.

Bolsonaro’s Liberal party, or PL, is now seeking to overturn the result, with a complaint filed on Tuesday that claimed to have found “serious and irremediable inconsistencies” in older models of Brazil’s digital ballot boxes.

A study commissioned by the PL said a software defect meant it was not possible to individually identify machines manufactured before 2020, which accounted for almost 60 per cent of all those used in the poll.

Consequently, it argued, votes cast through these machines should be “invalidated”, a move the authors said would hand victory to Bolsonaro.

While the development is the first clear sign that Bolsonaro intends to formally contest the electoral failure in a manner similar to that of Donald Trump in the 2020 US presidential vote, there was scepticism about the chances of the effort succeeding.

High-ranking Bolsonaro allies have already accepted his defeat and Lula has been internationally recognised as the winner.

Rather, political analysts believe it is a tactic by the rightwing nationalist to appeal to his supporters, many of whom believe — without evidence — that the election was fraudulently won by Lula.

Although roadblock demonstrations against the election result have mostly died down at Bolsonaro’s own request, a hard core of supporters has continued to hold protests outside army barracks, urging military intervention to prevent Lula taking office.