London: London Mayor Boris Johnson urged British government ministers to join the campaign to leave the European Union in a newspaper interview on Saturday, again defying Prime Minister and fellow Conservative David Cameron.
A political showman who is widely thought to be keen to succeed Cameron, Johnson said he wanted to change the minds of the majority of cabinet ministers who favour voting to remain in the EU in a June 23 referendum on the issue.
"People should look at the arguments. I have huge respect for what the Prime Minister is saying. But people I think should think about the arguments," Johnson told the Telegraph.
In a separate interview with the Times newspaper, Johnson dismissed the argument that a "leave" vote could spark last-ditch talks to achieve a better settlement for Britain inside the EU, resulting in a second referendum.
Asked whether there could be another referendum, Johnson told the paper: "No. Out is out."
Last week he had appeared to leave open the prospect of a second vote, arguing that the EU "only really listen to a population when it says No". That prompted Cameron to tell parliament on Monday that the idea of a second referendum was one "for the birds".
Opinion polls have differed about the likely outcome of the referendum, with the uncertainty sending sterling to a seven-year low against the dollar this week.
The latest poll, published on Friday by ORB for the Independent newspaper, showed support for the "out" campaign had risen to 52 per cent from 48 per cent from a month ago, while support to stay in the EU had fallen to 48 per cent from 52 per cent.
Cameron and Johnson have been friends since attending Oxford University together in the 1980s, but also rivals. In a thinly veiled jab at Johnson over the referendum, Cameron also told parliament on Monday: "I am not standing for re-election, I have no other agenda than what is best for our country."
Meanwhile, in Shanghai, British finance minister George Osborne pushed financial leaders from the top 20 economies to include the risk of Britain leaving the European Union in their list of dangers to the world economy on Saturday, gaining explicit support from the United States.
In a significant boost for Cameron and Osborne, US Treasury Secretary Jack Lew expressed clear support for Britain's continued membership of the EU.
"Our view is that it's in the national security and economic security of the United Kingdom, of Europe and of the United States for the United Kingdom to stay in the European Union," Lew told a news conference.
"This is an issue that will be decided by the voters of the United Kingdom in June and we certainly hope that (they) reach that conclusion," Lew added, in unusually direct comments on foreign political matters.
The final G20 communique, seen by Reuters, lists "a shock of a potential UK exit from the European Union" as one of the risks to the global economy, alongside volatile markets, cheap commodities and the migration crisis.
"It was the British who called for it, but it didn't meet with opposition," one G20 official said. "Everyone around the table would rather avoid a shock of that sort at such a fragile time for the global economy."
Osborne said finance ministers and central bank governors raised "serious concerns" about a British departure from the EU.
"They have concluded unanimously today that what they call the shock of a potential UK vote to leave is among the biggest economic dangers this year," he said.
Some G20 officials also saw the inclusion of the line on Britain in the communique as a way to draw attention to the negative consequences of exiting the EU to support Cameron's campaign to stay in.
Italian Finance Minister Pier Carlo Padoan said a decision by Britain to leave the EU, which it joined in 1973, would have negative global consequences.
"We would classify a UK exit from the EU as a powerful geopolitical shock, a negative shock," he told reporters in Shanghai.
The City of London is a major global financial centre, accounting for roughly 10 per cent of Britain's gross domestic product (GDP) and some bankers think leaving the EU could disrupt business and force many financial institutions to move out.
Opinion polls in Britain differ over the likely outcome of the June 23 referendum. Uncertainty about Britain's future in Europe sent its currency to a seven-year low against the US dollar earlier this week.