The Institute for Fiscal Studies has warned that government borrowing will rise, public sector spending cuts will increase. The OECD has also said the UK must do more to boost growth and tackle inequality, which it says are key to economic recovery.
The OECD said the UK economy may need more stimulus and a further round of quantitative easing may be necessary.
The OECD said UK growth remained flat, and is only expected to "pick up momentum" towards the end of next year. The Paris-based economic think tank forecasts that the UK economy will grow just 0.9% this year, after shrinking 0.1% in 2012.
Angel Gurría, the OECD's secretary general, said a "particularly bright spot" in the UK was employment figures.
Some of the key players have praised her landmark speech - but critics say it is too light on detail and time is running out to sign a deal.
A comparatively quiet reception greeted the launch of the new iPhone 8 and 8 Plus - a far cry from the crowds of years gone by.
Footage shows the dangerous rescue effort after the family were left at the mercy of the sea on a boat overturned by Hurricane Maria.