Ivanka Trump, the president's daughter and a top White House adviser, sent hundreds of emails about government business from a personal email account last year, the Washington Post reported Monday.

The emails were sent to White House aides, cabinet members and Ivanka Trump's assistants, many in violation of public records rules, the newspaper said.

U.S. President Donald Trump mercilessly criticized his 2016 Democratic rival, Hillary Clinton, for using a private email server during her time as secretary of state, labelling her "Crooked Hillary" and saying she belonged in jail.

Today, he called the report "fake news," though he did admit his daughter sent the emails from her personal account.

"They weren't classified like Hillary Clinton. They weren't deleted like Hillary Clinton. There was no servers in the basement like Hillary Clinton had," he told reporters outside the White House. He added that all of the emails in question are in the presidential records.

A spokesperson for Ivanka Trump's lawyer, Abbe Lowell, didn't dispute the Washington Post report.

"While transitioning into government … Ms. Trump sometimes used her private account, almost always for logistics and scheduling concerning her family," said the spokesperson, Peter Mirijanian.

Messages deleted, then 'retained'

Mirijanian stressed that no classified information was transmitted in the messages, that no emails were deleted and that the emails have since been "retained" in conformity with records laws.

"When concerns were raised in the press 14 months ago, Ms. Trump reviewed and verified her email use with White House counsel and explained the issue to congressional leaders," he said.

Despite the attempt to downplay the report, Elijah Cummings, top Democrat on the House of Representatives' oversight committee, said the committee would investigate the matter when Democrats gain control of the House in January.

"We plan to continue our investigation of the Presidential Records Act and Federal Records Act, and we want to know if Ivanka complied with the law," Cummings, from Maryland, said in a statement.

Cummings in October 2017 expressed concern about the admitted use of personal email during the transition by Trump and her husband, Jared Kushner, a senior adviser to the president. Cummings, in a letter addressed to the couple at that time, requested they preserve all records to ensure they were in compliance with federal law.

The discovery was prompted by public records requests from the liberal watchdog group American Oversight. The group's executive director, Austin Evers, said in a statement that "the president's family is not above the law," and he called on Congress to investigate.

"For more than two years, President Trump and senior leaders in Congress have made it very clear that they view the use of personal email servers for government business to be a serious offence that demands investigation and even prosecution, and we expect the same standard will be applied in this case," he said.

The emails the group uncovered include correspondence between Ivanka Trump and Linda McMahon, head of the Small Business Administration, and between Trump and Education Secretary Betsy DeVos.