Morten Messerschmidt, a European lawmaker and one of the country's most ardent eurosceptics, was kicked off the populist party's top leadership late on Tuesday after the DPP agreed to pay back 500,000 kroner (67,000 euros, $74,000) of EU funds.
"It's sloppiness at a very high level," party leader Kristian Thulesen Dahl told public broadcaster DR.
The money had been used to cover expenses for two EU conferences that appeared to be indistinguishable from the party's regular summer meetings, as well as an educational trip to Brussels for campaign workers during a public holiday when EU institutions were closed.
Cash had also been spent on media training and an advertising campaign. Messerschmidt told broadcaster TV 2 News that he "completely rejects that there has been a deliberate attempt to cheat."
The expenses scandal is a sharp blow to the outspoken politician, who helped the eurosceptic DPP become Denmark's largest party in the European Parliament election of 2014.
The liberal Politiken daily responded by publishing a list of DPP expense quotes, accusing the EU of wasting taxpayers' money.
"If Europeans knew the full extent of the shameless waste of money, I am convinced that there would be a revolution," Messerschmidt wrote in 2012.
The European parliament had previously asked the DPP to pay back 2.9 million kroner that it spent on political campaigning. The party repaid 1.6 million kroner in June, saying it did not administer the rest of the money.
Messerschmidt previously sat on the board of the Movement for a Europe of Liberties and Democracy, a now defunct conservative European alliance.
Last year, the DPP paid back 120,700 kroner to Brussels after using the money to tour Danish harbours on a sailing ship a few months before local elections in 2013.