British government says it has no contingency plans for possible Scottish breakaway

LONDON (Reuters) - The British government said on Monday it was not drawing up contingency plans for a surprise vote in favour of Scottish independence, less than three weeks before Scotland holds a referendum on whether to leave the United Kingdom.

Voters in Scotland will decide on Sept. 18 whether they want to form an independent state with opinion polls showing Scots are likely to vote to keep their 307-union with England intact.

However, one survey last week showed the anti-independence campaign's lead had halved following a televised debate and experts say that the unique nature of the vote - the first of its kind in British history - makes it unusually difficult to predict.

The debate has raised big questions such as what currency an independent Scotland would use and what would happen to Britain's Scotland-based nuclear submarines. But the government on Monday refused to discuss how it would handle a split.

"No such work (is being) undertaken," Prime Minister David Cameron's official spokesman told reporters when asked if the government had drawn up contingency plans for a "Yes" vote.

"The government's entire focus is on making the case for the UK staying together."

(Reporting by William James; Editing by Andrew Osborn)