Boris Johnson cements position as leading Conservative party rival to David Cameron with provocative call to cut income tax for Britain's highest earners Boris Johnson delivered a provocative challenge to David Cameron and George Osborne today to cut income tax for Britain's highest earners. The Mayor of London's call came after he burnished his Tory leadership credentials yesterday with an assured and joke-studded speech received rapturously by the party faithful. Although he was careful to pour praise on Mr Cameron, he cemented his position as the Prime Minister's leading rival with a passionate plea for Britain to head into a new "age of enterprise" and a list of his achievements running the capital. Later he reached out to the party Right by repeating his demand for the top rate of tax to be lowered - although he acknowledged it would be "politically very difficult to deliver now" and "would not be easy at a time people are suffering." Mr Osborne provoked a storm when he cut the top rate from 50p to 45p in this year's Budget, but ministers have made clear that it will not be cut further. But Mr Johnson warned that Britain was competing "with one hand tied behind our back compared to other tax jurisdictions, which are extremely challenging for us at the moment." The Mayor told the BBC: "We're getting into a situation where we are tax-uncompetitive." In his conference speech, his second appearance in a 24-hour visit to Birmingham that stole the limelight from Mr Cameron, he took a swipe at the Government for failing to tackle the problem of airport capacity in the South-east of England. He also poked gentle fun at the Prime Minister for failing recently to be able to translate the phrase "magna carta." The Mayor delighted his audience with a stinging attack on "semi-Marxist taxpayer-funded Chateauneuf du Pape-swilling tax minimisers" and told activists who helped him to re-election this year: "You showed that we can overcome a Labour lead and win in the places which the two Eds are so cocky as to think that they own." He told Mr Cameron, who was watching him, that he was doing a "fantastic job" in "clearing up the mess" left by the last Labour government. Mr Johnson declared: "It is the historic function of Conservative governments over the last 100 years to be the household implements on the floor of the house, so effective at clearing up after the Labour binge has got out of control." The Mayor called for the "can do" attitude of the Olympics to be applied to the economy, with British firms becoming "gold medal winners." And he pointed to the diversity of products made in London as evidence that the entrepreneurial spirit was alive and well in Britain. "Go to Soho and see them doing the special effects for so-called Hollywood movies," he said. When they eat cake on the Champs Élysées, they eat cake made in London. When they watch Gangnam-style [dancing] on their TVs in Korea, they watch it on TV aerials made in London. The Dutch ride bicycles made in London. The Brazilians use mosquito repellent made in London. Every single chocolate Hobnob in the world is made in London," he declared to laughter and applause." Boris on... the Olympics: Boris on... pre-Olympic gloom: The buses were on strike, the taxi drivers were blockading the West End, one of them actually handed the keys of his cab to a police guy and jumped off Tower Bridge ... Boris on... David Cameron: I was pleased to see you called me a blond-haired mop in the papers. Boris on... helping the "strivers": As Napoleon almost said, Britain is a nation of small and medium-sized enterprises. We need to think every day what we can do to create the right conditions for them to flourish to become more than medium-sized, to become gold medallists in the UK, in the global, economy. Ken Livingstone: "I don't think Ken is going to come back from that one - he just got a clap from the Tory party conference, if that hasn't finished him nothing will."al, economy."