The FTSE leapt to a six-month high on Thursday thanks to bumper corporate results across Europe and the US and a strong showing from miners.
The FTSE 100 rose 0.5% to 5,757.22 in early trading, despite negative company announcements across various sectors.
Government borrowing hit a record high in September, with the biggest deficit for the month since records began in 1993.
Shadow Chancellor Alan Johnson says Osborne's Spending Review amounts to a "reckless gamble with people's livelihoods" and accused the government of being motivated by ideological reasons.
UK equity markets and sterling were largely unfazed by today's Spending Review with investors unsuprised by the level of the cuts.
The coalition government has announced a staggering £81bn in spending cuts, but can the economy take them?
Read George Osborne's full Spending Review statement to Parliament.
Equitable Life with-profts annuitants (WPAs) will be paid in full from a £1.5bn compensation pay-out, with the first payments coming next year.
HM Revenue & Customs (HMRC) will receive a budget boost of £900m to crackdown on tax avoidance and claw back money owed.
The Comprehensive Spending Review is necessary to bring the UK economy "back from the brink", says Chancellor George Osborne.