“Corporate” Democrats in the Senate imperil Joe Biden’s Build Back Better Act, a leading House progressive warned – but not just Joe Manchin and Kyrsten Sinema, the targets of most leftwing ire.

Such Democrats, Rashida Tlaib of Michigan said, are influenced by donors who “don’t have the best interests of the American people in mind”.

At the same time, the New York Times reported that Manchin and Sinema are increasingly receiving money from corporate and conservative donors.

The president’s domestic spending package is worth $1.75tn and seeks to increase spending on social programs and healthcare and to combat the climate crisis.

After months of negotiation, and after Biden signed into law a $1.2tn bipartisan infrastructure bill, the House of Representatives passed Build Back Better on Friday.

There was no Republican support and there will be none in the Senate. That gives Manchin of West Virginia and Sinema of Arizona huge influence, in a chamber split 50-50 and controlled by the vote of Vice-President Kamala Harris.

The two senators have already pressured the Democrats to cut the cost of the spending plan in half.

Tlaib is one of the first Muslim women in Congress, representing the third-poorest congressional district.

In an interview broadcast on Sunday, she told Axios she was “fearful” that “corporate Dems” would “guide this agenda. It’s gonna be the people that are gonna continue to profit off of human suffering.

“I know that they’ve been influenced and guided by folks that don’t have the best interests of the American people in mind.”

Tlaib said she was referring to Manchin and Sinema, “but I think there are some others that … have issues with the prescription drug negotiations there.

“And so I can’t say it’s just those two. They seem to be leading the fight, but I wouldn’t be surprised if folks are hiding behind them.”

Manchin has spoken regularly, mostly painting the spending plan as too expensive. Sinema is less vocal but on Friday she gave an interview to ABC15, an Arizona station.

Saying she was “a workhorse, not a show horse”, she said she welcomed progressive criticism.

“I appreciate the first amendment,” she said. “So I appreciate when folks are willing to tell me they agree with me or disagree with me. If they want to protest, if they want to offer things, all of that is welcome.

“So I guess my message to folks would be keep telling me what you think. I appreciate it. And I’m going to keep doing the work and delivering results for Arizonans.”

Sinema said she would not “bend to political pressure from any party or any group”.

In terms of financial pressure, the New York Times reported on Sunday that Manchin and Sinema were attracting support from “conservative-leaning donors and business executives”.

Kenneth Langone, a Wall Street billionaire, usually gives to Republicans but has praised Manchin and promised to fundraise for him.

Langone told the Times: “My political contributions have always been in support of candidates who are willing to stand tall on principle, even when that means defying their own party or the press.”

Stanley Hubbard, a billonaire Republican donor who has given to Sinema, said: “Those are two good people – Manchin and Sinema – and I think we need more of those in the Democratic party.”