Free Democratic Party (FDP) MP for Berlin Lars Lindemann posted images on Tuesday comparing the Greens' election pledge to get canteens to serve only vegetarian food one day a week to the Nazis.
Images from a Nazi propaganda poster were uploaded with the Green Party's logo on Mr Lindemann's Facebook page, but soon disappeared.
The poster showed a mother serving food to her blonde children, with the caption: “Eat wholegrain bread as it is better and healthier.”
Nazi chiefs launched the campaign to encourage Germans to reduce their reliance on imported wheat in 1939.
Mr Lindemann told The Local that he realised the poster was Nazi propaganda but denied comparing the Green Party to National Socialism.
“This doesn't mean that I think the Green Party are Nazis,” he said. But he added that by telling people what they could eat on certain days the policy did carry hallmarks of totalitarianism and as a liberal he completely disagreed with it.
“No one should tell me what I should eat on a certain day,” he said. FDP chiefs have also attacked the policy but Lindemann's posters were a step too far for the party and a spokesman apologised.
The Green Party's proposal to ban meat in canteens one day a week on a so-called ‘Veggie Day' has provoked fierce criticism. Michael Fuchs, deputy chairman of the conservative Christian Democrats group in parliament, railed against the notion of having an individual decision taken away.
"Bit by bit, according to their [the Greens'] image of society, the state assumes more and more functions, decrees more and more bans," he said in a statement.
"What a presumptuous plan," said Bild newspaper. "Whoever wants responsible citizens must also treat them that way. And must not constantly try to re-educate them."
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But the Greens argue that reducing meat consumption would have health benefits in a country known for its love of sausages, as well as an upside for animal protection and climate change.
Their manifesto for the September 22nd elections calls for public cafeterias to take on a "trailblazing" role.
A spokesman for Consumer Affairs Minister Ilse Aigner told reporters on Monday that the trend in recent years in Germany had shown less meat was being eaten, but he said that a "balanced" diet was what was called for. "Meat is also part of that," he said. "We generally don't have much truck with paternalism," he added.