Theresa May’s deputy spokesman distanced the prime minister from the suggestion that it could cost £66bn a year in tax revenues if Britain leaves the single market and has to rely on World Trade Organisation rules.
“These figures that have been quoted today aren’t new; they were around some time ago,” the spokesman said. “I’m not going to get into reheating the arguments that were made during the referendum campaign.
“The emphasis now on getting best possible deal – to recognise that the country has clearly voted to leave the European Union. It is now incumbent on the government to make sure that process happens – and that we are mindful there must be no attempt to thwart or stall that process.”
The comments were in response to claims that figures from a projection in April, which said GDP could fall by 9.5% if the UK had to revert to WTO rules, had been used in a new document drawn up by civil servants for cabinet ministers.
The claims infuriated Brexit-supporting MPs, who argued that the Treasury assumptions in April had changed, and that civil servants were scaremongering in an attempt to block a full departure from the EU.
Stewart Wood, a Labour peer who used to work for the former chancellor and prime minister Gordon Brown, said it felt as though the Treasury was conducting a “guerrilla war inside the government against hard Brexit”.
A Treasury source refused to confirm the existence of the paper, and said the figures were old. May’s spokesman said the government was focused on preparing a negotiating position as it got ready to trigger Article 50.
He did not deny that the assumptions on which the Treasury forecasts had been based had since changed and said the government would be refreshing its analysis of the potential impact of Brexit on the economy.
“That kind of work is ongoing now ... and will go on for the remainder of this year and into next year, before we trigger Article 50. What you’ll see is an effort to make sure exactly where we are negotiating positions.”
He said the government was “looking ahead” and was focused on getting the best possible deal. He admitted there would be some economic turbulence as Britain left the EU but said the economy remained strong and efforts were being made to protect it during the process.
He refused to comment on the decline in the value of sterling, but said the currency did fluctuate.
