LONDON -- Scotland's pro-independence leader says a separate Scotland would not be a foreign country to England, and claims U.K. Treasury chief George Osborne made a "monumental error" when he said Scotland could not keep the pound as its currency after independence.

First Minister Alex Salmond told a London audience that Scotland and the rest of the British Isles are inseparably bound.

Scots will vote in an independence referendum on Sept. 18. Salmond says a "yes" vote will mean a country with its own passports, taxes and fairer social policies. But he wants to keep Britain's currency, its monarch and European Union membership.

He said Tuesday that "Scotland will not be a foreign country after independence, any more than Ireland, Northern Ireland, England or Wales can ever be foreign countries to Scotland."