Trump denies knowledge of Kushner's WhatsApp messaging

US President Donald Trump on Friday denied any knowledge of son-in-law and senior adviser Jared Kushner's alleged use of an encrypted messenger app for official White House business.

"I know nothing about it. I've never heard that. I've never heard about it," Trump told reporters outside the White House before leaving for meetings at his Florida estate.

House Oversight Chairman Elijah Cummings sent a letter to White House Counsel Pat Cipollone on Thursday, saying that he had learned from Kushner's lawyer, Abbe Lowell, that Kushner has used WhatsApp, a Facebook Inc-owned messaging application, for official work, including with some foreign officials.

Cummings said he had also learned from Lowell that Ivanka Trump, the president's daughter and senior adviser, is still receiving work-related emails on her personal email account and did not always forward them to her official White House account.

In an email to Cummings on Thursday, Lowell denied that he ever told the Democratic chairman Kushner had ever communicated with foreign officials, and that he had followed the proper protocol for classified information.

He also denied having told the House panel that Ivanka Trump does not forward relevant personal emails.

The US Presidential Records Act prohibits senior White House officials from creating or sending a record "using a non-official electronic message account."

During the 2016 campaign, Trump frequently lashed out at Hillary Clinton, then Democratic presidential candidate, for her use of a private email server while serving as secretary of state. Federal investigators launched an investigation against Clinton but brought no charges.