The House Oversight Committee has focused on Hunter Biden’s work for businesses based in countries such as Ukraine and China while his father served as US vice-president from 2009 to 2017. So far they have turned up no evidence of wrongdoing by the elder Biden.

The panel also invited three of Hunter Biden’s former business associates to testify.

“Mr Biden’s counsel received Rep Comer’s letter late today and will respond in writing,” Hunter Biden’s legal team said in a written statement on Wednesday evening.

James Comer is the chair of the Oversight Committee.

Hunter Biden, who has worked as an investor and lawyer and sold his own paintings, testified in a closed-door interview last month as part of the inquiry. He had initially said he would only testify publicly, but reversed course after lawmakers threatened to hold him in contempt.

In the hours-long interview that at times turned contentious, he said repeatedly that his father had no involvement with and drew no benefit from his own business activities.