He described recent economic changes, including the economic advances made by Asian nations, rising oil prices and the current financial crisis as the biggest change since the Industrial Revolution.

"This last week will be studied by our children -- as the week the world was spun on its axis -- and old certainties were turned on their heads," he said.

Brown has been hit by sinking poll numbers and lost by-elections and from inside the party. Some recent polls, however, suggest the economic challenge and Brown's handling of it have made him less unpopular.

In his speech, Brown reviewed Labor achievements since Tony Blair became prime minister in 1997 and promised policies that would protect Britain from the current economic upheaval and build "the fair society of the future."

"And we should never forget one thing -- that every single blow we have struck for fairness and for the future has been opposed by the Conservatives," he said.

In an unusual and unannounced move, Brown was introduced by his wife Sarah.