Former prime minister John Howard has hit out at the size of Queensland's public service, undermining Opposition Leader Tim Nicholls' promise not to cut jobs.

The Liberal Party elder statesman campaigned alongside LNP MP Tarnya Smith in her marginal Brisbane electorate of Mount Ommaney on Friday as he joined the state campaign for the first time.

Former prime minister John Howard said Queensland has too many public servants despite LNP leader Tim Nicholls promising no cuts. Credit:Sitthixay Ditthavong

Asked about Queensland's rising debt problem, Mr Howard said economic growth and activity would help eliminate money that was owed but also said a slimmer public service would reduce the burden.

"You also eliminate debt by not just appointing unnecessarily large numbers of state employees," he said.