Mr Hockney had opposed London's controversial congestion charge
One London party candidate Damian Hockney has quit the race to be mayor of London, blaming a lack of media opportunities for parties such as his.
The 51-year-old said "smaller groups" were "effectively barred" from certain types of campaigning, such as TV advertising and mailshots to voters.
Rules meant broadcasters each offered only one pre-election "slot", he added.
Mr Hockney, a London Assembly member, was a vice-chairman of UKIP and deputy leader of breakaway group Veritas.
He said there were far more opportunities for larger political parties during an election campaign such as the London race.
"As a smaller group, we are effectively barred from writing by means of the laws, for example, to every single voter in London.
"We are barred from TV advertising and we are barred from getting the message across above a certain level of spin," he told BBC London 94.9.
He also claimed the mayoral race was "a media election, fought just in the media".
"It is not being fought on policies," Mr Hockney, who remains an assembly member, added.
"It is being fought on a smear and counter-smear campaign between the two major candidates, and within that, the media gives patsy coverage in order to achieve this balance."
He said that guidelines followed by broadcasters, which are designed to ensure TV, radio and online coverage of the election campaign is balanced between the rival candidates, were "a disaster for democracy".
"The BBC, ITV - they give a kind of what I would call uncritical patsy coverage in order to achieve that balance, and within that there is no room for the minor parties," he said.
Their approach left him "appalled and horrified" because they were unfair "from the point of view of the minor parties", Mr Hockney added.
"It's been treated as a kind of a balance thing rather than as a journalistic thing."
Any candidate wishing to run for mayor must pay a £10,000 deposit by Friday, refundable if they secure 5% of first-choice votes in the election on 1 May.
Asked if he had withdrawn from the race because he felt he might lose any deposit he put down, Mr Hockney insisted this was "totally incorrect".
"It's nothing to do with that, of course," he said.
Mr Hockney has also resigned as one of the 23 members of the Metropolitan Police Authority, the body which holds the larger of London's two police forces to account.
Although the One London party will no longer have a representative running for mayor, it will field candidates in the London Assembly election, also being held on 1 May.