LONDON - The British government minister responsible for Scotland warned on Sunday nationalists could win an independence referendum this year because of complacency among those campaigning to hold the United Kingdom together.Speaking ahead of a Sept 18 vote that will decide whether Scotland breaks its three-century-old union with England, Alistair Carmichael, Britain's Secretary of State for Scotland, said nationalists had a huge ‘war chest’ to fund their campaign and appeared more "hungry" for victory."The biggest danger for the United Kingdom camp in this whole argument is that people look at the polls. They show us with a healthy lead consistently. As a consequence they think this is not going to happen," Carmichael told BBC TV. "Well I've got to tell everybody it could."Opinion polls have long shown Scots would vote to reject independence by a clear margin. But two recent polls suggested a small swing towards the nationalist camp, led by Alex Salmond of the Scottish National Party (SNP). A TNS poll on March 25 showed that 42 percent would reject independence, with 28 percent voting "yes" and 28 percent undecided.Carmichael, who was appointed in October last year to try to inject more passion into the campaign to keep the UK together, said the "no" camp - which includes all of Britain's three main political parties - had to step up its performance. "They (the nationalists) have got an unprecedented war chest to pour into this campaign. We've got to realise what is coming and as a consequence we've got to get our arguments in place and our campaign as sharp as theirs."He separately told The Observer newspaper there was a risk that "no" campaigners would wake up to the threat posed by the nationalists too late. "I am not expecting to lose, but it is eminently possible that they will be able to buy momentum with the advertising and campaign resource they have. If they do, it could all get very difficult."Carmichael was speaking a day after British finance minister George Osborne denied a newspaper report which quoted an unnamed minister as saying Scotland could be allowed to keep the British pound if it voted for independence, an issue at the heart of the Scottish secession debate. The SNP's Salmond said on Sunday the government's "panicky" rebuttal of the story showed its opposition to an independent Scotland using the pound was based on "bluff and bluster".