Michael Bloomberg will not accept political donations if he runs for president and will not take a salary if he wins, according to senior aides discussing the New York billionaire’s plans as he marches toward a formal 2020 announcement.

“He has never taken a political contribution in his life. He is not about to start,” chief adviser Howard Wolfson said in an interview. “He cannot be bought.”

The decision to refuse contributions would make it impossible for Bloomberg to participate in any sanctioned Democratic debates. Democratic National Committee rules require participants to meet a polling threshold and raise donations from tens of thousands of voters.

Nonetheless, one of the richest men in the world is sending every indication he has decided to enter the crowded primary. In recent days, he has created a campaign committee with the Federal Election Commission and qualified for the ballot in at least three states. His team has reserved more than $30m in television ads set to begin running on Sunday.

Just 10 weeks before voting begins in Iowa, the move reflects the former New York mayor’s concern that the Democratic field is not well-positioned to defeat Donald Trump next year.

I’m disgusted by the idea that Michael Bloomberg or any billionaire thinks they can circumvent the political process Bernie Sanders

Bloomberg’s wealth has emerged as a central issue as the political world awaits his formal announcement. He is estimated to be one of the 10 richest people in the world.

His Democratic rivals pounced on news of the massive TV ad buy and his decision to bypass the first four states on the primary calendar – Iowa, New Hampshire, Nevada and South Carolina – in favor of focusing on states that hold votes in March.

“I’m disgusted by the idea that Michael Bloomberg or any billionaire thinks they can circumvent the political process and spend tens of millions of dollars to buy elections,” the Vermont senator Bernie Sanders wrote on Twitter. “If you can’t build grassroots support for your candidacy, you have no business running for president.”

The Minnesota senator Amy Klobuchar swiped at Bloomberg as she campaigned in New Hampshire.

“He didn’t want to deal with all of this grassroots campaigning from the beginning, you know that’s on him,” she said. “I think this is important.”

She added: “I think that you want to have a candidate for president who’s willing to go out, day after day, and talk to regular people like this.”

Bloomberg’s team insists his wealth allows him to be more responsive to everyday people because he isn’t beholden to special interests. Wolfson said Bloomberg would work for only $1 a year as president, as he did as New York mayor for more than a decade.

Bloomberg’s message on money is much the same one employed by Trump in his 2016 campaign, although Trump accepted millions in donations. Trump now donates his salary each quarter to different departments of the federal government.

Bloomberg “is wholly independent of special interests, will not take a dime in any contribution, and never has in any of his three races”, Wolfson said, adding that any money Bloomberg spends on his presidential run will come from his own pocket.

Wolfson said he was willing to spend “whatever it takes to defeat Donald Trump”.