"Voters are learning that contrary to your claim to always stand with middle-class workers, you have instead chosen to stand with large corporations and against workers," Brown wrote.
Warren, a consumer advocate, said Wednesday that since she went into public service in 2008, she's made financial disclosures and released her client contacts.
But she has declined to release details about other firms she performed legal work for earlier. Asked Monday on WTKK-FM if she could produce a list of those firms, she said, "I don't have it."
Brown said Harvard Law School requires faculty members to report outside activities each year.
Warren also faulted Brown for refusing to release the names of lobbyists he's met with since winning the 2010 special election to fill the Senate seat left vacant by the death of longtime Democratic Sen. Edward Kennedy.
"I am surprised to hear Senator Brown raise an issue around disclosure when Senator Brown clearly has many things that he has not wanted to disclose on his own," she said.
In the new video posted Wednesday, supporters' war cries are heard escalating as Brown criticizes Warren's claims of Native American heritage. Brown doesn't react in the brief clip, posted by the Democrat-leaning Blue Mass Group.
The group posted a video on Tuesday showing staff members for Brown and the state Republican Party shouting war whoops and performing tomahawk chops during a rally days earlier in Boston's Dorchester neighborhood.
Brown spokeswoman Alleigh Marre issued a statement Wednesday saying Brown "regrets that members of his staff did not live up to the high standards that the people of Massachusetts expect and deserve."