She will take the helm next month at the third-biggest government comms department after the Ministry of Defence and the Department for Trade and Industry.
Diamond will oversee a 130-strong comms team, which includes a 23-strong press office plus staff covering internal comms, exhibitions, publications, marketing and web comms.
She reports to Defra director-general of corporate services Mark Addison and department permanent secretary Brian Bender.
Diamond replaces Lucian Hudson, who left after three years last July to join the Department for Constitutional Affairs, where he is responsible for comms around the Freedom of Information Act.
Four years after the last foot and mouth epidemic, Defra this week came under fire from Conservative MP Edward Leigh, who accused the department of not planning adequately enough for a future outbreak.
He also accused the department’s cattle-tracing system for being seriously flawed.
In 2001, foot and mouth forced farmers to slaughter more than six million animals and cost the farming and tourism industries millions of pounds.
The department – at the time known as the Ministry for Agriculture, Fisheries and Food – rebranded after the crisis with an additional environment brief.
Prior to the DfES, Diamond was head of Welfare to Work Marketing at the then Department for Education and Employment. She has also been publicity commissioner at BBC Broadcast and has held several posts within the NHS.
Defra’s acting head of communications Kelly Freeman will return to her post as deputy director of comms when Diamond arrives.