A United States backpacker has blasted New Zealand's clean and green image as a "myth", highlighting issues with trash, polluted waterways and cars.

Marius Viktorius, from Michigan, has been travelling through New Zealand over the past four months.

He has kept a blog of his travels, writing about his adventures including freedom camping, friendly locals and Maori culture.

However, now his trip has come to a close, he said the country's environment did not live up to the advertising campaign.

"What's the first thing that comes to mind when you think of New Zealand?" he asks.

"Millions of sheep on rolling hills, stunning mountains, or pristine rivers maybe?"

All he had seen from Lord of the Rings, Instagram photos and the 100% Pure marketing campaign had left him with the impression New Zealand was a " green, sustainable, and clean country".

"Plastic and trash are abundant, and though there is recycling, it's not [ingrained] in the culture.

"As a byproduct, the culture creates a lot of trash and they haven't found a sustainable solution for disposing it, or curbing its consumerist culture."

Although New Zealand had some of the "most amazing natural phenomenon", farming, consumerism and tourism were impacting it, he wrote.

"While New Zealand boasts many of the world's remaining clean rivers, they're getting increasingly polluted.

"This problem resembles the environmental degradation in most parts of the world."

Much of the native bush had been cleared.

"Today a tiny fraction of the native bush remains."

However, he did enjoy learning more about Maori culture and meeting friendly New Zealanders.

"The more time I spent here, the more I saw just how friendly the locals are, especially the Maori.

"Many a time I'd be hitchhiking in the evening when someone would pick me up and invite me to stay with them.

The times I did they'd cook dinner and spend the night with me. All those times I was baffled and wondering, 'Why do they trust me? They just met me!'. They did and I'm grateful for it.

"All things considered, we should not look at New Zealand as a role model for pure nature. Instead, we should look at it as a role model for a trusting people."