Jared Kushner, President Trump’s son-in-law and a White House senior adviser, has used his personal email account to conduct official government business, his lawyer acknowledged on Sunday.

The lawyer, Abbe Lowell, said that Mr. Kushner, using the personal account, had received or sent “fewer than a hundred emails” involving his White House colleagues over the first seven months of the administration. Mr. Lowell said the emails were all forwarded to Mr. Kushner’s official account, creating a record.

The use of the personal account was first reported by Politico.

Mr. Kushner is not the only official in the Trump White House who has been found to have used private email or text messaging for government business, a situation that has raised questions about the administration’s preservation of records. But Mr. Kushner is the person closest to the president to have his personal email use become public.

As a candidate, Mr. Trump aggressively attacked Hillary Clinton, the Democratic nominee, for her use of private email while she was secretary of state. Some of Mr. Trump’s allies outside the White House are urging him to press for a prosecution of Mrs. Clinton, even though an F.B.I. investigation into her handling of classified information has been closed. At Mr. Trump’s rallies, his supporters still break into cheers of “lock her up!”