Mr Johnson called for an end to such gloomy talk just hours after Mr Cameron said he would continue to take “big, difficult decisions” on the deficit, while helping businesses to grow.
The Prime Minister promised to sweep away rules, reviews and checks that are holding companies back.
The Mayor, who is tipped as a potential future leader, urged the Government to go further in its efforts to support an “age of enterprise” by cutting personal tax rates and exempting new homes from stamp duty.
He told business leaders the Coalition should collect more money from companies such as Google instead of considering “absurd” plans for a mansion tax on individuals. “We should have taxes that are low but fair and it is absurd to be suddenly whacking up taxes on cash-poor people who happen to inhabit expensive houses in London when firms like Google are paying zero,” he said.
“Neither arrangement strikes me as being fair and so Google and co face a very clear choice — they can either change their tax arrangements or do much more to serve our society by visibly taking on 18 to 24-year-olds who are out of work.”
He said high personal tax rates in Britain mean that Andy Murray pays a greater proportion of his winnings to the taxpayer than any tennis player in the world. “I am afraid that high rates of personal taxation are likely to make us less competitive,” he will say.
“In the 19th century London became the biggest and richest city on earth because of its openness to trade and to talent.
“I am worried that we are losing some of that openness at a critical time.”
The Coalition is still considering Lib Dem proposals for higher taxes on the rich. Speaking on the BBC’s Andrew Marr at the weekend, Vince Cable, the Business Secretary, insisted it is being taken seriously at the highest levels of the Government.