The House select committee investigating the Capitol attack is considering issuing a subpoena to Ivanka Trump to force her cooperation with the inquiry into Donald Trump's efforts to return himself to power on 6 January, according to a source familiar with the matter.

Any move to subpoena Ivanka Trump and, for the first time, force a member of Trump's own family to testify against him, would mark a dramatic escalation in the 6 January inquiry that could amount to a treacherous legal and political moment for the former president.

The panel is not expected to take the crucial step for the time being, the source said, and the prospect of a subpoena to the former president's daughter emerged in discussions about what options remained available after she appeared to refuse a request for voluntary cooperation.

But the fact that members on the select committee have started to discuss a subpoena suggests they believe it may ultimately take such a measure – and the threat of prosecution should she defy it – to ensure her appearance at a deposition on Capitol Hill.

The select committee did not address a possible subpoena for Ivanka Trump at a closed-door meeting last Friday, and the panel wants to give her a reasonable window of opportunity to engage with the investigation before moving to force her cooperation, the source said.

The panel would also have to formally vote to move ahead with such a measure, the source said, and Thompson would probably inform the House speaker, Nancy Pelosi, of the decision before formally authorizing a subpoena to the former president's daughter.