Leaving the European Union might cost the U.K. 100 billion pounds ($145 billion) in lost economic output and 950,000 jobs by 2020, the Confederation of British Industry said as it stepped up its campaign against a so-called Brexit. A vote to leave the bloc in the referendum Prime Minister David Cameron has called for June 23 “would cause a serious shock to the U.K. economy,” Britain’s main business lobby group said, citing a study it commissioned from PricewaterhouseCoopers of two Brexit scenarios. “Leaving the European Union would be a real blow for living standards, jobs and growth,” CBI Director-General Carolyn Fairbairn will say in a speech in London Monday, according to remarks released in advance by the lobby group. “The savings from reduced EU budget contributions and regulation are greatly outweighed by the negative impact on trade and investment.” According to the study, U.K. GDP might be 5 percent lower than it would otherwise be by 2020 in the case of withdrawal, though it might only be 3 percent lower if a free-trade deal is rapidly reached with the rump EU. Growth might be as low as zero in 2017 or 2018, the CBI said. ‘Smaller Economy’ “The economy would slowly recover over time, but never quite tracks back to where it would have been,” Fairbairn will say. “Leaving the EU would mean a smaller economy in 2030.” The CBI said last week it will campaign to keep the U.K. inside the EU after a survey found four-fifths of its members believe this would be best for their businesses. Brexit campaigners argue Britain would be better off outside the bloc because Europe is a shrinking market for U.K. exports and the government would be able to conclude its own trade deals with fast-growing economies around the world. “The EU funded CBI are desperate to recreate the same scare stories they spread when they urged Britain to scrap the pound and join the euro,” Matthew Elliott, chief executive of Vote Leave, which is campaigning for an exit, said in a statement. “They were wrong then and they are wrong now.”