Britain's main political parties struck what they said was a historic deal to grant Scotland tax-raising powers and greater autonomy to try to satisfy disappointed separatists who lost an independence vote two months ago.

The deal, which was unveiled Thursday but will not be implemented until after a U.K.-wide parliamentary election next year, amounts to the biggest transfer of powers to Scotland from the United Kingdom since 1999, when a Scottish parliament was set up.

Britain's three main political parties promised to grant Scotland more powers in a last-ditch attempt to shore up support for the union days before a referendum in September in which Scots ultimately spurned independence.