James criticised over UKIP hustings absence
The favourite in UKIP's leadership race has been accused by another candidate of "undemocratic" campaign tactics by refusing to take part in debates.
Diane James has not appeared at any hustings, saying she can answer more of activists' questions at her own events.
But her rival Philip Broughton said her stance was "bang out of order".
The winner of the leadership contest, triggered by the resignation of Nigel Farage, will be announced on 15 September.
MEP Bill Etheridge, councillor Lisa Duffy and activist Elizabeth Jones complete the line-up.
Mr Broughton, a former Conservative councillor and UKIP parliamentary candidate, said: "I'm not happy with the tactics of no debate; no communications, no openness - which is what a leadership debate should be all about.
"This is supposed to be about the future direction of the party and one candidate is stopping that from happening."
He added: "It's unopen, undemocratic and bang out of order".
Ms James, UKIP's deputy chairwoman and justice and home affairs spokeswoman, defended her absence from hustings in a recent BBC interview.
She said there was "no need" for her to debate with her rivals, saying her own programme of events around the country allowed her to take more questions from party activists.
"I am more interested in what will convince individual members and activists that I have got an answer to their direct questions."
Mr Broughton said he was not making a "personal attack" on Ms James, but added that "members need to know what's going on".
Mr Etheridge joined the criticism on Thursday, accusing Ms James of conducting a "coronation tour" rather than a campaign and telling her: "Get down off your thrown and have a debate."
As well as the UKIP-organised debates, Mr Broughton and Mr Etheridge both claimed they had been asked to be involved in two BBC hustings which were now not going ahead as planned after Ms James declined to be involved.
These were on the Victoria Derbyshire programme and on BBC Essex, Mr Broughton said.
The BBC said the Victoria Derbyshire programme hosted a UKIP leadership debate on 2 August 2016 and would continue to report developments in the contest as they happen.
It is understood that the programme had not confirmed or scheduled a follow-up hustings and any discussions about them were speculative.
BBC Essex is understood to have changed the format of its coverage after Ms James and another candidate declined to take part.
Ms James said she had not been notified that the hustings had been cancelled and declined to comment further.