Sen. Elizabeth Warren warned President-elect Donald Trump against choosing “Wall Street insiders” for top financial posts, likely previewing the confirmation battles to come in the Senate.

In a letter to the president-elect dated Tuesday, the Massachusetts Democrat specifically noted three members of the Trump transition team with ties to Wall Street and “demonstrated records of failure during the 2008 financial crisis” whom she would find unacceptable for top positions: David Malpass, Paul Atkins and Steve Mnuchin.

Mr. Malpass, a former Bear Stearns chief economist, is working on shaping Mr. Trump’s Treasury Department, which Mr. Mnuchin is a leading candidate to lead. Mr. Atkins, a former Securities and Exchange Commission commissioner during the George W. Bush administration, is working to fill the ranks of financial regulatory agencies in the Trump administration.

Ms. Warren made similar comments Tuesday at The Wall Street Journal’s CEO Council event in Washington, saying the involvement of corporate lobbyists and business leaders contradicted Mr. Trump’s campaign promises to shake up the Washington establishment.

Representatives for Mr. Trump and his transition operation didn’t respond to a request for comment.