George Osborne has said Moody's message is "explicit" to carry on with austerity.
He says "we can either abandon our efforts to deal with debts" or we can "redouble our efforts" and make a brighter future for our children.
More top news
The Duke and Duchess of Cambridge met young people who have battled mental health issues on Saturday.
Former Chancellor Lord Geoffrey Howe was Margaret Thatcher's longest-serving Cabinet minister, also taking on the role of Foreign Secretary.
Lord Geoffrey Howe is known by many for his resignation speech which was seen as the catalyst which destroyed Margaret Thatcher.