Shares in Standard & Poor's parent group McGraw-Hill have slumped after an Australian court ruled S&P's AAA ratings misled investors during the financial crisis.
Standard & Poor's has cut Spain's credit rating by two notches to one level above junk status, warning the government's policy options are limited as economic recession deepens.
BlackRock's iShares has launched the first ETF to offer exposure to global AAA and AA rated government bond exposure.
London's leading share index is edging back up towards the 5,800 mark in early trading, recovering from a fall to a three-week low at the end of last week as Spanish bailout fears weighed on sentiment.
M&G's co-head of fixed income Jim Leaviss has warned the UK could face losing its AAA rating on 5 December, the day of the Autumn Statement, as the growing budget deficit could force George Osborne to abandon plans for fiscal consolidation.
Moody's will strip the US of its AAA rating if a deficit reduction deal is not struck in Congress, it has warned.
AstraZeneca has named Pascal Soriot, Roche's chief operating officer of pharmaceuticals, as its new chief executive officer.
European markets rose in early trading as investors awaited a meeting on Greece's future and possible anti-crisis action from policymakers.
Moody's has said new ESMA guidelines on ETF stock lending are "credit negative" for asset managers and will hit profitability - but will also spark an uptick in investor interest.
J.P. Morgan's Nick Gartside and Barings' Alan Wilde have warned the UK's AAA-status is at risk of downgrade following the shock contraction in the second quarter's GDP.