Seven hundred National Party billboards across the country were altered by activists in a co-ordinated operation overnight.
The activists fixed new slogans over the billboards which say: "The Rich Deserve More" and "Drill it! Mine It! Sell it!"
An un-named organiser of the operation told The Aucklander National needs to be more honest in its campaign, and the new slogans reflect the truth which it says National is neglecting to mention.
"We decided to help the National Party spell out its plans in ways that every voter can understand. They believe in increasing the deficit by giving the rich tax cuts, then selling state assets to reduce the deficit they just created, drilling oil wells along our coastline, and digging up forests for low grade coal. We want to make sure voters know that.
"Over 50 people have been improving National's billboards in Auckland, Wellington, Gisborne, Whakatane, Napier, Hastings, New Plymouth, Palmerston North, Kapiti Coast, Nelson, Marlborough, Motueka, Golden Bay, Christchurch and Dunedin.
"We hope voters like the more truthful billboards and hope that some National supporters will want to leave them as they are.
"The Prime Minister believes in transparency. He says he doesn't lie. We're happy to help."
The National Party's law and order spokeswoman, Police Minister Judith Collins, said she was not aware of the billboard alterations.
"Every election, some of my billboards get stolen and I report them to the police."