Boris Johnson was entitled to refer to gay men as “tank-topped bum boys” because of his right to “free speech”, a Tory candidate says.

Chris Philp, a justice minister, defended the prime minister’s notorious comment – and said he personally was not offended because he is not homosexual.

Instead, he described it as “colourful language”, before saying he was not prepared “to give a running commentary" on his bosses’ statements.

“How offensive would Boris Johnson have to be before you said don’t say it,” asked LBC presenter Eddie Mair.

Mr Philp replied: “I’m not going to tell anyone what to say because I believe in free speech.”

The candidate, in Croydon South, was put on the spot after Mr Johnson himself defended his phrase, used in a 1998 column about the resignation of Peter Mandelson.

He wrote: “Weep, O ye shirt-makers of Jermyn Street, ye Cool Brittannia tailors and whatever exists of human finer feeling. In the Ministry of Sound, the tank-topped bumboys blub into their plis.”

On live TV last week, Mr Johnson refused to apologise or accept he had caused offence, saying only that he had “never intended to cause hurt or pain to anybody”.

On the LBC show, Mr Mair said one questioner was asking: “Why should the LGBT [lesbian, gay, bisexual and transgender] community vote for a leader who referred to gay men as tank-topped bum boys?”

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Mr Philp attempted to deflect the conversation onto David Cameron’s legalisation of gay marriage, arguing: “Actions speak louder than words.”

When asked if it was offensive, Mr Philp said: “I'm not from the LGBT community,” – prompting Mr Mair to respond “Oh, you have to be from the LGBT community to find that offensive?”

At one point, Mr Mair asked: “Is bum boys OK? Would you use that expression?”

“I personally wouldn't, no, but I'm not going to tell Boris what words he should use” the Conservative responded.

“Why because he's your boss?” asked Mair back. “No, because people can use their own language and they can make their own judgements,” Mr Philp insisted – before using the “free speech” defence.

Earlier, Labour attacked the prime minister’s “dark ages” attitudes after highlighting remarks he made in a Spectator column on single mothers.