The mayor of London, Boris Johnson, has dismissed the £250,000-a-year he earns from a controversial second job as “chicken feed”.

Johnson also insisted it was “wholly reasonable” for him to write newspaper columns on the side because he did them “very fast”.

The comments risk infuriating millions of Londoners struggling to make ends meet amid the economic downturn.

They are also unlikely to please David Cameron, who has ordered his shadow cabinet to give up extra work in the run-up to the general election to show their “commitment”.

Johnson, who is paid nearly £140,000 for his day job, was questioned over his lucrative contract with the Daily Telegraph during an interview for the BBC’s HARDTalk programme.

He responded “It’s chicken feed.”

Pressed on whether voters would agree with that description, the mayor said he was being “frivolous”.

But he went on: “I happen to write extremely fast. I don’t see why on a Sunday morning I shouldn’t knock off an article, if someone wants to pay me for that article then that’s their lookout and of course I make a substantial donation to charity.

“Maybe that money shouldn’t go to charity, maybe you’d rather I didn’t make those contributions to charity. It seems to me to be a wholly reasonable thing to do.”

Johnson said: “I think that frankly there’s absolutely no reason at all why I should not, on a Sunday morning before I do whatever else I need to do on a Sunday morning, should not knock off an article as a way of relaxation.”

Johnson decided to continue with his columns for the Telegraph after being elected last year, but donates £50,000 from his annual fee to charities.

Liberal Democrat frontbencher Norman Baker said: “There is nothing wrong with people writing newspaper columns but this is an enormous amount of money and for Boris Johnson to dismiss it as ‘chicken feed’ shows just how out of touch he and the Conservative party are from the reality of life for millions of Londoners struggling to make ends meet in the depths of a recession.”