British Prime Minister David Cameron has said that leaving the European Union will cost Britain billions in infrastructure investment.
He said a vote for Brexit would mean an end to Britain's membership of the European Investment Bank (EIB) which has poured more than £16bn into UK projects in the past three years.
Mr Cameron said that withdrawal from the EIB would have a "devastating impact" on future infrastructure projects.
"Vital projects across every region of the UK have been financed by the EIB. These make a huge difference locally, nationally, and sometimes globally," he said in a statement.
"Not only would leaving the EU see us wave goodbye to this crucial funding - but, with a smaller economy hit by new trading barriers and job losses, it's unlikely we'd be able to find that money from alternative sources.
"Infrastructure affects the competitiveness of every business and the prosperity of every family in the country - but a Leave vote on June 23 risks putting the brakes on the infrastructure investment we need and shifting our economy into reverse."
Among projects to have benefited from EIB support, he said, were the purchase of new super express trains for the East Coast Main Line, the extension of the M8 motorway between Edinburgh and Glasgow, and the expansion of Oxford University's research and teaching facilities.
Mr Cameron's comments came as Jeremy Corbyn urged voters to blame the Conservatives - not the EU - for Britain's economic difficulties as he sought to rally Labour supporters behind the Remain campaign.
While the two rival leaders were out campaigning in a common cause, they had sharply differing messages.
At a rally in London, Mr Corbyn launched a highly partisan attack on the Conservatives, saying responsibility for many of the country's problems "lies in 10 Downing Street, not in Brussels".
His comments are likely to be seen as a response to concerns within the Remain camp that they are encountering significant hostility to the EU on the doorstep in traditional Labour areas.
The Labour leader, who for many years opposed EU membership, highlighted the importance of European regulations in underpinning workers' rights, which would be jeopardised by a Leave vote.
"It is not the European Union that is the problem here, it is the Conservative government," he said.
"Their agenda is to end the working time directive, their agenda is to take away that protection, their agenda is to take away the four weeks' holiday we won all across Europe. Their whole concept is of undercut, undercut, undercut. Increase profit at one end, increase misery at the other end."
He added: "Do we allow xenophobes to take over or do we instead occupy that political and intellectual territory of the idea that you can solve things together? You'd better build those alliances working with people rather than isolating yourselves from them."
