Prime Minister David Cameron promised "the best of both worlds" as he made his final appeals to voters in Thursday's referendum to remain in a reformed European Union.
"For the sake of our children and grandchildren, vote Remain tomorrow," Cameron said Wednesday as he attended a series of campaign events west of London.
He visited a company selling skateboards with senior Labour politician Harriet Harman in the south-western city of Bristol, before travelling to a house-building firm in nearby Swindon, a garden centre and a school in Oxfordshire, and a hospital in Solihull in the West Midlands.
Cameron told BBC Radio 4 that he rejected "the idea you have to choose between being a success in the European single market of 500 million and campaigning to have jobs and wealth created by trading with other economies."
"You don't have to choose, you should do both," he told the broadcaster. "The vision of Britain in Europe is, we do have a special status; we have the best of both worlds."
Cameron said he had "set out a very positive case that we're stronger, safer and better off if we stay."
The Leave campaign has focussed on EU migration in the last few weeks, but Cameron said Britain could not "solve our immigration problem by leaving the European Union."
He said he wanted to re-examine EU freedom of movement after negotiating concessions in February that allow Britain to restrict payment of welfare benefits to some EU migrants.
"We are reopening the freedom of movement directive because of the renegotiation, and we're getting changes on criminals, on third-party nationals, on sham marriages; on a whole set of issues that have come out of court judgments frustrating the United Kingdom," Cameron said, adding that "reform continues on Friday."
But European Commission President Jean-Claude Juncker, speaking to reporters in Brussels, warned Britain there would be "no kind of renegotiation."
"We have concluded a deal with the prime minister, he got the maximum he could receive and we gave the maximum we could give," Juncker said.
"So there will be no kind of renegotiation, nor on the agreement we have found ... in February, nor as far as any kind of treaty negotiations are concerned," he said. "Out is out."
Speaking during a visit to north-eastern England, Vote Leave co-leader Boris Johnson said Juncker's intervention "tells you all you need to know about the conceit of the European Union officials."
"But it also tells you that nobody who thinks there's any point in staying in and fighting for change from within is going to get what they want," Johnson told reporters.
"The idea that we can do better by staying in the EU and fighting for change is, I'm afraid, a sham, a snare and a delusion," he said.
In a letter to readers of the popular free tabloid Metro, Johnson said the EU was "undemocratic, bureaucratic and unrepentant for its failings."
"Tomorrow you have a once-in-a-lifetime opportunity to take back control," he said. "To lift our eyes beyond the strangulation of the EU, to cooperate and trade not just across the European continent but with the rest of the world."
In a counter appeal to Metro readers, Cameron appealed to undecided voters not to "take the risk of leaving."
"Choose strength, safety and prosperity - today, and for many years to come," he wrote.
Nigel Farage, leader of the anti-EU UK Independence Party, said Juncker's statement "confirms this is Britain's last chance saloon."
"This is one vote that can really change things," Farage said on Twitter. "Vote for your country. Vote to leave the EU."