Lawyer says offer is in response to Republican efforts, led by President Trump, to unmask the whistle-blower.

The United States official, whose whistle-blower complaint led to the impeachment inquiry against President Donald Trump, has offered to answer written questions submitted by House Republicans, his lawyers said.

The surprise offer on Sunday, made to Devin Nunes, the top Republican on the intelligence committee leading the inquiry, would allow Republicans to ask questions of the whistle-blower without having to go through the committee’s Democratic chairman, Adam Schiff.

Lawyer Mark Zaid said the whistle-blower would answer questions directly from Republican members “in writing, under oath & penalty of perjury”, part of a bid to stem escalating efforts by Trump and his allies to unmask the person’s identity.

Only queries seeking the person’s identity will not be answered, he said, adding the Republican bid to expose his client’s identity “could jeopardise their safety, as well as that of their family”.

“We will ensure timely answers,” he said.

6/So we have offered to @DevinNunes, Ranking HPSCI Member, opportunity for Minority to submit through legal team written questions to WBer. Qs cannot seek identifying info, regarding which we will not provide, or otherwise be inappropriate. We will ensure timely answers. — Mark S. Zaid (@MarkSZaidEsq) November 3, 2019

Nunes’ office did not have immediate comment.

The proposal came as Trump called on the whistle-blower to come forward in a stark departure from norms in such cases.

The whistle-blower had raised concerns about Trump’s July 25 call with Ukrainian President Volodymyr Zelenskyy in which he pressed Zelenskyy to investigate Trump’s political rivals. That call became the catalyst for the impeachment inquiry.

The whistle-blower’s secondhand account of the call has been providing a plan for House Democrats investigating whether the president and others in his orbit pressured Ukraine to probe political opponents, including former Vice President Joe Biden.

“Reveal the Whistleblower and end the Impeachment Hoax!” Trump tweeted.

Later on Sunday, he pushed the news media to divulge the whistle-blower’s identity, asserting that the person’s accounting of events is incorrect.

“The whistle-blower should be revealed because the whistle-blower gave false information,” Trump told reporters at the White House. “He made up a story.”

The whistle-blower’s complaint has been corroborated by people with first-hand knowledge of the events who have appeared on Capitol Hill.

“They know who it is. You know who it is. You just don’t want to report it,” Trump, who denies any impropriety, told reporters. “And you know you’d be doing the public a service if you did.”