Philippine presidential favourite Rodrigo Duterte has brushed off controversies over an alleged secret fortune and a rape joke to keep a huge lead going into the final days of the election campaign, a pollster said on Friday.

Duterte has faced a barrage of last-minute attacks ahead of Monday's election over allegations he hid millions of dollars in undisclosed bank accounts, while his critics have repeatedly warned he is a dictator in the making.

A self-confessed serial adulterer, the 71-year-old also generated outrage last month when he joked at a campaign rally that he had wanted to rape a "beautiful" Australian missionary who was sexually assaulted and murdered in a 1989 Philippine prison riot.

As with other controversies - which included calling the pope a "son of a whore" - none appears to have impacted his popularity, according to the Social Weather Stations survey released on Friday.

Duterte has an 11-percentage-point lead over his nearest rival, Senator Grace Poe, Social Weather Stations said, equal to recent polls conducted before the accusations he had amassed a secret fortune. Duterte denies those allegations.

Duterte has 33% support, with Poe at 22 and administration pick Mar Roxas at 20%.

In the Philippines, a president is elected simply by who gets the most votes.

Duterte has gained support across all sectors of society by fashioning himself as an anti-establishment politician who can achieve quick fixes to deep-rooted problems, such as crime and poverty.

His campaign manager, Leoncio Evasco, accused critics on Friday of scare-mongering, and described the election as a "war of the classes".

"All the innuendos, attacks, and mud thrown at us and our candidate, are acts of desperation, of panic and of cowardice," Evasco said in a statement.

"The fear they are hoisting is to camouflage their own fear of losing power over us."

Duterte, mayor of the southern city of Davao, has vowed to end crime within six months of his presidency by ordering security forces to go on a killing spree. He has vowed to kill tens of thousands of criminals.

Duterte has been accused of running vigilante squads in Davao that have killed more than 1,000 suspected criminals. At times he has boasted about his involvement but on other occasions denied any links to the vigilantes.

Television ads began airing on Thursday in which children hit out at Duterte's jokes about raping the Australian missionary, as well as his cursing, notably against the pope.