The FTSE is slightly down in early trading, with RBS hit by fears it may be exposed to Ireland's economic problems.
Lord Young has replaced Lord Sugar as the government's enterprise tsar, tasked with cutting red tape for small businesses and encouraging new start-ups.
The US federal reserve could pump up to $1trn of extra QE into the economy to battle unemployment and encourage growth.
The UK's credit rating has been revised from negative to stable by S&P, further consolidating its ‘AAA' status and boosting the coalition government's economic plans.
Read George Osborne's full Spending Review statement to Parliament.
George Osborne today criticised the regulation of banks under Labour and outlined plans to introduce a permanent annual levy.
The index of the UK's 100 leading shares has closed down on the day, with major insurers the biggest drag on markets.
Federal Reserve chairman Ben Bernanke has given his strongest signal yet that he will begin another round of quantative easing in the US.
The FTSE continued to feed off global optimism in early trading on Thursday, extending yesterday's 1.5% gain.
The pound has fallen to a five month low against the euro amid a rising claimant count and falling consumer confidence.