There were two separate call-outs in areas of Preston – one at Plungington and the other one at Deepdale – in which firefighters needed to put out fires after rubbish was set ablaze.
They were minor incidents but crew manager Mick Hayes, who is based at Preston, said: “They are putting lives at risk when they do this.
"It usually relates to fly-tipping when either the people who have dumped the stuff, or someone else, sets fire to it.
"But if that happens just before a more serious incident, it pulls fire engines away when they could be tackling the bigger job.
"There is a potential cost when they start these fires.”
Only four people have been prosecuted for fly tipping in Preston in the past two years, despite more than 5,000 reports about waste being dumped illegally in the city.