Britain's Daily Telegraph newspaper has come out in favour of quitting the European Union, urging voters to tick the "Leave" box in the referendum on 23 June.
The Telegraph, which has a daily circulation of nearly 500,000, joins The Sun, The Sunday Times and its own sister Sunday newspaper in the Leave camp.
The Telegraph made its declaration in an editorial titled "Vote leave to benefit from a world of opportunity".
It comes as sterling soared against the dollar and euro on easing fears that Britain will vote to break with the EU, as recent polls showed growing support for staying in the EU.
Three days before the critical referendum, the pound jumped 2.3% to $1.4675. It surged roughly 2% to 77.08 pence per euro.
Analysts cautioned that sentiment on Brexit likely would be volatile amid the heated rivalry of the campaigns, with the "leave" and "remain" camps running neck-and-neck, according to poll results released over the weekend.
Meanwhile, it has emerged that civil servants told British Prime Minister David Cameron four years ago that it was "impossible" for the government to meet its immigration promises while the UK remained in the EU, Mr Cameron's former policy guru has said.
Civil servants said "directly and explicitly" that the pledge to reduce net migrations to the tens of thousands would fail, according to Steve Hilton.
Just weeks ago Mr Cameron insisted he stuck by his "ambition" of bringing net migration into the UK - which last month hit 333,000 - below 100,000.
Mr Hilton said the premier reaffirmed his commitment to target in the 2015 general election even though he "had been told was undeliverable".
Writing in The Daily Mail, the Leave campaigner recalled the details of a meeting in the final months of his time as director of strategy.
He said: "We were told, directly and explicitly, that it was impossible for the Government to meet its immigration target as long as we remained members of the EU, which of course insists on the free movement of people within it."
Mr Hilton added: "You don't need to sit in a 'stock take' meeting at No 10 Downing Street to see the obvious truth: our immigration system is completely broken, and as long as we're in the EU, our elected governments are powerless to fix it.
"In the 2015 Conservative manifesto, the Prime Minister reaffirmed his commitment to the immigration target he had been told was undeliverable.
"When I saw that, I assumed this was either because he was certain he could negotiate a solution within the EU, or was assuming we would leave.
"For the Government to continue to make the promise today, after no negotiated solution was achieved and while campaigning to stay, is, I think, what (Michael) Gove and (Boris) Johnson meant when they described this as corrosive of trust in politics."
Corbyn says EU must change if UK voters reject Brexit
Labour Party leader Jeremy Corbyn has conceded voters "may well" back Brexit but insisted he would not take the blame if Britain severs its ties with Brussels.
Mr Corbyn told how he is "not a lover" of the EU and called for it to change "dramatically" if the UK does stay in.
Facing an audience of young voters on Sky News, Mr Corbyn said there was no "easy way back" if the country votes to quit.
"If we remain, I believe Europe has got to change quite dramatically to something much more democratic, much more accountable and share our wealth and improve our living standards and our working conditions all across the whole continent," he said.
"I'm not a lover of the European Union. I think it's a rational decision. We should stay in order to try and improve but does that change my views on points I've raised on public ownership of railways and things like that? Absolutely not."
Mr Corbyn, a long-time critic of the EU who voted against membership of the European Economic Community in 1975, has faced accusations that his campaigning for the Remain camp has been lukewarm.
Asked if he would shoulder some of the blame if Britain votes to quit, he replied: "I'm not going to take blame for people's decisions. There will be a decision made on Thursday. I'm hoping there is going to be a Remain vote, there may well be a Remain vote, there may well be a Leave vote."
Told he did not sound "too keen" on the EU, he replied: "Whatever the result we have got to work with it."
Mr Cameron insisted it would be "wrong and foolish and unwise to leave the single market altogether" and said that quitting the EU would be "irreversible".
Defending the tone of the campaign, he told the BBC: "I think there are real risks and I don't for one minute hold back from talking about those risks."
Both sides of the referendum have faced criticism over the way they have responded to the brutal killing of Jo Cox.
Ukip leader Nigel Farage accused Mr Cameron of a "despicable" attempt to use the much-loved Labour's MP's death to boost his chance of winning Thursday's EU referendum, an accusation the Prime Minister fiercely denied.
Remain campaign chief Will Straw was attacked after it emerged that he had told team members "we need to recognise that people have been pulled up short by Jo Cox's death".
Leave.EU chief Arron Banks, meanwhile, defended his decision to carry out polling on the impact the death may have had on voting intentions in the referendum.
The Ukip donor told LBC that he did not believe the move was tasteless, adding: "We were hoping to see what the effect of the event was."
George Osborne said he believes Leave is losing support because Mr Farage has "taken over" the campaign.
The Chancellor told LBC: "I have got lots of people I know very well in the Leave campaign and they didn't want to start off this campaign where they got to the position with only a couple of days to go to polling where Nigel Farage appeared to be their principal spokesman.
"But they have allowed him to take it over. They have allowed him to just talk endlessly about foreigners and immigration and of course there are concerns about immigration but it is not the only issue at stake in this referendum.
"I think he misjudges the mood of the nation."
Mr Osborne said that even a narrow victory for Remain on June 23 would mean the Europe question would be "resolved" for a generation.
Asked if he would suspend trading on the FTSE in the event of possible market turmoil following a Brexit vote, Mr Osborne replied: "The Bank of England and the Treasury, Governor (Mark) Carney and myself, we have of course discussed contingency plans but the sensible thing is to keep those secret and make sure you are well prepared for whatever happens."
