(CNN) Bernie Sanders harshly criticized the wealth of US senators during his first campaign for office in 1971, calling it "immoral" that half the members of the Senate were millionaires.

Sanders' decades-old comments, which were picked up in December 1971 by the Bennington Banner, a local Vermont newspaper, are resurfacing as the US senator from Vermont has acknowledged that he is now a millionaire in large part due to his 2016 best-selling book, "Our Revolution."

In a statement to CNN, Sanders campaign spokesman Josh Orton said, "Yes, it is true: Senator Sanders said in the 1970s that it is immoral that the government too often represents the interests of the super-wealthy and large corporations — and yes, it is also true that Senator Sanders has continued to demand a change from that for his entire life."

Orton continued, "As the son of an immigrant who grew up living paycheck to paycheck, Senator Sanders believes elected officials should represent the interests of working people, not corporations, special interests or the ultra-wealthy. This view has guided his work in politics, not the pursuit of personal wealth. Senator Sanders' family has been fortunate, and he is grateful for that because he knows the stress of economic insecurity. That is why he works every day to ensure every American has the basic necessities of life, including a livable wage, decent housing, health care and retirement security."

Sanders defended his newfound wealth in an interview with the New York Times. "I wrote a bestselling book," Sanders said. "If you write a bestselling book, you can be a millionaire too."

According to the Bureau of Labor Statistics, taking inflation into account, $1 million in 1971 is nearly $6.2 million in 2019. According to the Center for Responsive Politics, a nonpartisan research group that tracks money in politics, more than 70% of senators were millionaires as recently as 2015.

Sanders made the comments when he was running for US Senate at the time under the banner of the Liberty Union Party, a self-described "radical political party" that advocated nationalization of industries and redistribution of wealth to tackle inequality.

The senators serving at the time, Sanders said, advocated "the interests of corporations and big business ---- their fellow millionaires."

In the same article, Sanders proposed eliminating the annual salary of members of Congress (which was $42,500 in 1971) and instead replacing their pay with whatever the average income was in their home state. At the time, Sanders said it would amount to $7,600 for representatives from Vermont.

"I think the result would be that this country would immediately stop wasting billions on weapons which never get off the drawing boards, and on the support of military dictatorships throughout the world," Sanders said in the Banner, "I also have a feeling that a lot of tax loopholes that the corporations and millionaires receive would soon disappear."

Facing both Republican and Democratic opposition, Sanders' third-party campaign for senator earned less than 3% in the January 1972 special election. Sanders would run for office three more times under the Liberty Union banner before leaving the party in 1977. In his race for governor, later in 1972, he attacked the wealth of his opponents. Sanders lost each election in the 1970s, never earning more than 7% of the vote.

"Either they (the candidates) are millionaires to begin with or they get it from the corporations," Sanders said in September of that year, adding that senators refused to take on corporations.