The judge presiding over the Georgia prosecution of former US president Donald Trump and others for efforts to overturn the 2020 election has set a hearing on a motion alleging Fulton County district attorney Fani Willis has been romantically involved with a special prosecutor she hired for the case.

In an order on Thursday, Fulton County Superior Court Judge Scott McAfee set a February 15 hearing and ordered prosecutors to file their response by February 2.

The allegations have been seized upon by Mr Trump and other critics of the prosecution, who have argued that the case is tainted and should be tossed out.

Defence lawyer Ashleigh Merchant, who represents former Trump campaign staff member and one-time White House aide Michael Roman, made the allegations in a motion filed last week.

She alleged that Ms Willis was involved in a romantic relationship with lawyer Nathan Wade that created a conflict of interest and led to Ms Willis profiting personally from the prosecution.

The motion seeks to have the indictment thrown out and to have Ms Willis and Mr Wade removed from the case.

Ms Willis defended her hiring of Mr Wade and his qualifications during an address at a church in Atlanta on Sunday but has not commented publicly on the allegation of a romantic relationship.

Among other things, she cited Mr Wade’s 10 years of experience as a municipal court judge and 20 years in private practice.

Ms Willis’s office has said it will respond to Ms Merchant’s motion in a court filing but has not provided a timeline for that.

Ms Merchant has not provided any solid proof to support the alleged inappropriate relationship.

She mentioned “information obtained outside of court filings” and “sources close” to Ms Willis and Mr Wade.

Ms Merchant’s motion also mentions that filings in Mr Wade’s pending divorce are sealed but that she has filed a motion to unseal them.

A coalition of news organisations, including The Associated Press, filed a motion on Tuesday to gain access to those filings.

Ms Merchant wrote that Mr Wade has been paid large sums and has used some of his earnings to take Ms Willis on holiday to Napa Valley, Florida and the Caribbean.

She said that amounts to the pair “profiting significantly from this prosecution at the expense of the taxpayers”.

Ms Merchant said she can find no evidence that Mr Wade – whose law firm website touts his experience in civil litigation, including car accident and family law cases – has ever prosecuted a felony case.

She questioned his qualifications to try this case.

Mr Trump and Mr Roman were indicted by a Fulton County grand jury in August along with 17 others.

They are accused of participating in a wide-ranging scheme to try to illegally overturn the 2020 presidential election in Georgia.

Four of those charged have already pleaded guilty after reaching deals with prosecutors.

Mr Trump, Mr Roman and the others who remain have pleaded not guilty.

Mr Roman was the director of Election Day operations for the Trump campaign and had also worked in the White House.

Prosecutors say he helped co-ordinate an effort to contact state legislators on Mr Trump’s behalf to encourage them to “unlawfully appoint presidential electors”.

He is also alleged to have been involved in efforts to have Republicans in swing states that Mr Trump lost, including Georgia, meet on December 14 2020 to sign certificates falsely saying Mr Trump had won their states and that they were the electors for their states.

He was in touch with local Republican officials in several states to set up those meetings.

The Washington Post first reported the scheduling of the hearing.