An anti-Donald Trump protester has defended his fellow demonstrators after it emerged a majority who were arrested by police in Portland last week had not voted.

State election records show only 30 per cent of the 112 detained in Oregon’s capital had actually cast their ballot, according to local TV network KGW.

At least 79 reportedly did not vote, or were not even registered as voters in the state.

But one unnamed protestor told the television station it was not fair to look at only those arrested.

“You just look at your sample and it’s the people who got arrested,” he said.

“And the people who got arrested. I just don’t think they’re representative of the majority of the people who are out protesting.”

Following the election of Mr Trump, thousands of people took to the streets in Portland for five straight nights.

Police declared a riot on Thursday evening, with an estimated of $1 million worth of damage to property.

Kevin Grigsby, one of the 112 arrested, defended his decision not to vote: "I did not (vote) and the reason why is because we know the electoral college is really what matters the most.

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“And I think that we need to change that because your vote doesn’t matter if you don’t have enough electoral college points.”

KGW made a list of all 112 people arrested by Portland police during recent protests. Their names and ages were then compared to state voter logs.

The records reportedly showed 39 could have voted but failed to, while 35 were not registered to vote.

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It remains unclear if protesters who were not registered to vote in Oregon were registered in other states, but most did give Oregon addresses as their official residence.

Portland has been the centre of some of the most ardent protests against the president-elect.