Smith will step into the role of executive director of government comms on an interim basis until the end of the year following the departure of Grey, who will join Citigroup.
Field, meanwhile, will be leaving David Cameron to become the UK's next executive director of the International Monetary Fund (IMF).
Of Grey’s replacement, minister for the Cabinet Office Francis Maude said:
‘Jenny spearheaded the reforms to government communications we introduced in 2010. As a result, the operation is now leaner, more agile and more strategic – and will deliver more efficient communications for the taxpayer. I wish Jenny well in her new role and thank her for all her work.
‘The appointment of Godric Smith as interim executive director of government communications will enable us to continue delivering these important reforms. As a former prime minister's official spokesman, and with his excellent work at the Olympic Delivery Authority and as director of government communications for London 2012, Godric brings the experience and expertise needed for this important role. I look forward to working with him to deliver effective communications that represent value for taxpayers’ money.’
Grey's departure comes after she oversaw the creation of the post-COI government comms frameworks, the first of which has launched.
Today's announcement also follows shortly after the Government revealed that it planned to spend an estimated £285m on comms during the financial year 2012-13.
Smith takes on the role having worked on the Olympics over the past seven years as director of communications for the ODA.
Before this, he worked at Downing Street from 1996 to 2006, including as the Prime Minister's official spokesman between 2000 and 2004.
A process to appoint Field’s successor is under way and an appointment will be made in the coming weeks. He will join the IMF towards the end of the year.