Boris Johnson defended his foul-mouthed outburst at a black cab driver today, saying he was merely 'getting the ball back over the net' by telling the man to 'f*** off and die'.

The London Mayor was defiant as he left his home this morning after footage of the heated exchange emerged overnight.

Refusing to apologise, the Tory MP described his enraged reaction to the driver's heckling as 'a gentle attempt to return service.'

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Defiant: Boris Johnson refused to apologise for the outburst as he left his London home today, instead describing his choice words as a 'gentle attempt to return service'

'It comes under the heading of getting the ball back over the net,' he told reporters this morning before cycling off.

The driver had been been badgering Mr Johnson over his handling of black drivers' complaints about the taxi app Uber.

Footage of their exchange was obtained last night in which the politician is heard telling the man to 'f*** off and die - and not in that order,' as he cycled home.

It was just after midnight and Mr Johnson was cycling home along St John’s Street in Islington, North London, after attending a dinner, when the cabbie saw him driving the same way and decided to heckle him.

The driver was apparently irate over the mayor’s perceived lack of support for black-cab drivers in their battle with controversial minicab booking firm Uber.

He seized the opportunity to give Mr Johnson his opinion by leaning out of his cab window and gesticulating vigorously with his hand, while simultaneously shouting: ‘You’re one of them, mate.’

Hitting back: The Tory MP said the tirade was about 'getting the ball back over the net' when questioned today

Exchange: The cabbie was apparently irate over London Mayor Boris Johnson’s perceived lack of support for black-cab drivers in their battle with controversial minicab booking firm Uber

In his direction: The driver seized the opportunity to give Mr Johnson his opinion by leaning out of his cab window and gesticulating vigorously with his hand, while simultaneously shouting: ‘You’re one of them, mate'

After dinner: It was just after midnight and Mr Johnson was cycling home in Islington, North London

Fighting back: Wearing a yellow cycling helmet with his trademark blonde mop poking out the sides, Mr Johnson swore at the startled taxi driver

Unhappy drivers: Mr Johnson was accused of ‘not having the guts’ to stand up to Uber, which is blamed for putting hundreds of black cabbies out of work in recent months

On two wheels: Mr Johnson (file picture) angered cabbies by suggesting they needed to accept they were being challenged by the powerful forces of the ‘free market’ and ‘consumer choice’

A video filmed by a passerby reveals the foul-mouthed response from Mr Johnson, who is tipped as a future leader of the Conservative Party.

HOW DOES THE UBER APP WORK? The Uber smartphone app has blamed for taking business away from licensed taxi drivers. With a few swipes of a smartphone screen, users can hail an Uber cab within three to four minutes. The app finds where they are by using the phone’s global positioning system and connects them with the nearest available driver. Uber then texts customers when their cab arrives. Customers can also view rates and enter pick-up and drop-off locations to get a quote for the trip. Users do not even need to use cash. Once they arrive at the destination, the fare is automatically charged to their credit card on file, and a receipt is emailed. Drivers take 80 per cent of the fare; the other 20 per cent goes to Uber. Yesterday afternoon, a journey by black cab from Trafalgar Square to Kensington Palace in London cost £15 on the meter. The same four-mile journey with Uber was quoted at £7 to £10. Advertisement

Wearing a yellow cycling helmet with his trademark blonde mop poking out the sides, Mr Johnson swore at the startled taxi driver.

The cabbie, continuing his vulgar hand gesture, repeats: ‘That’s what you are: one of them.’

This morning friends of the politician said he felt 'obliged' to respond with some 'choice words of his own.'

‘I believe this particular cabbie is a serial heckler,' a source said last night.

'He offered Boris a few choice words. Boris felt obliged to offer him a few in return. And off they went.’

Licensed Taxi Drivers Association spokesman Steve McNamara said: ‘The taxi drivers in London are rightly worried about the way that private firms are operating.

'I can understand why the driver had a pop at Boris, and to be fair to him, he gave back as good as he got.’

The onlooker who filmed the row on his iPhone said: ‘I didn’t expect Boris to use such select words – maybe if he is going to be the next Prime Minister he should calm things down a bit.’

Tensions between Mr Johnson and London cabbies came to a head last month.

Mr Johnson was accused of ‘not having the guts’ to stand up to Uber, which is blamed for putting hundreds of black cabbies out of work in recent months.