UKIP leadership hopeful Steven Woolfe has admitted failing to disclose a drink-driving ban when seeking election as a police and crime commissioner.
Mr Woolfe told Huffington Post he "forgot about the conviction" from 2002 when he stood for election in 2012 - in a possible breach of electoral law.
He got a £350 fine and nine-month ban for being drunk in charge of a scooter.
Mr Woolfe is awaiting UKIP's verdict on whether he can run for the leadership, having missed the nominations deadline.
The 48-year old MEP and immigration spokesman, who is seen as the frontrunner to succeed outgoing leader Nigel Farage, blamed technical issues with the registration site and insisted he was still in the race.
This has not been officially confirmed by the party, which is scheduled to announce the final list of candidates on Tuesday.
Other contenders to succeed Mr Farage are thought to include Huntingdonshire councillor Lisa Duffy and MEPs Jonathan Arnott and Bill Etheridge. MEP Diane James is also widely expected to throw her hat into the ring.
Asked about his prior conviction, Mr Woolfe told Huffington Post: "I made a foolish mistake 14 years ago which I regret. As the years went on I forgot about the conviction as I got on with my life.
"The conviction was a spent conviction in November 2012 and not in my mind when I stood for police and crime commissioner in Greater Manchester.
"It was also a spent conviction when I stood for the European elections in 2014 and general election in 2015."
Under electoral rules, police and crime commissioner candidates are required to declare convictions for which they could have received a prison sentence, and it is a criminal offence to make a false statement on nomination papers.
Mr Woolfe has also rejected claims that his party membership temporarily lapsed in 2014 - which could affect his eligibility to stand under the party's rules.
"It is false. On March 17 2011, I paid over £1,500 to the party. Part of that was to the patrons' club and the remainder was to have a five-year membership that ran out in 2016 in March," he said on Monday.
The leadership contest has been sparked by Nigel Farage, who led the party for most of the past eight years, standing down after the UK's vote to leave the EU.
A number of high-profile figures, including deputy leader Paul Nuttall, former deputy chair Suzanne Evans and UKIP's sole MP Douglas Carswell have ruled themselves out.
To stand, candidates each needed the backing of a proposer and 50 supporters from at least 10 UKIP branches - and to have been a member for the past two years.
The winner will be announced on 15 September.