An election-eve Liberal Party point-scoring attempt may have backfired, with claims that police were called to pre-polling stations over union "thuggery" seemingly fabricated.

Further allegations from the party's campaign headquarters that an ambulance was used as a "battering ram" by the paramedics' union to attack a Liberal candidate's car have also been denied.

Liberal campaign director Damien Mantach released a statement on Friday afternoon claiming United Firefighters Union members had bullied the party's Narre Warren North candidate at a pre-polling station.

"Amanda Stapledon was aggressively targeted, bullied and intimidated by the UFU to such an extent that police had to attend," the statement read.

The statement said police were also called in response to UFU members' "thuggish behaviour" towards former prime minister John Howard, who was campaigning for the Liberals in the marginal seat of Yan Yean on Melbourne's northern outskirts.