The leadership of former leftist president Luiz Inacio Lula da Silva's Workers Party (PT) on Wednesday approved former Sao Paulo governor Geraldo Alckmin as his running mate for Brazil's presidential election in October.

Lula, front-runner in the race against far-right incumbent President Jair Bolsonaro, has worked for months to round out his ticket with Alckmin, a center-right political veteran who ran unsuccessfully against Lula in 2006. He is expected to allay concerns from business interests about a return of a left-wing government.

The PT's national directorate voted 68 to 16 to approve Alckmin on the Lula ticket, a once-unimaginable union that aims to stop Bolsonaro getting re-elected.

Alckmin joined the Brazilian Socialist Party (PSB) last week so he could stand as Lula's vice-presidential candidate in an alliance with the PT.

The directorate's approval is expected to be confirmed by the part at a national meeting in early June.

In a statement, the PT made it clear that the alliance with the PSB and the Lula-Alckmin ticket was essential for a successful campaign to defeat Bolsonaro. Analysts say it will help draw the middle-class moderate voters uneasy about Lula's past corruption convictions.

The latest polls show Lula still ahead but Bolsonaro gradually eroding his leads lead in the race.

Alckmin, who governed Sao Paulo from 2001 to 2006 and again from 2011 to 2018, was a founding member of the Brazilian Social Democracy Party (PSDB), for decades a rival of the PT.

In the 2018 presidential race, he came fourth with just 4,76% of the votes. He left the PSDB party in December after 33 years.