The Open Government Partnership (OGP) is a coalition of 53 countries, with the UK serving as co-chair this year. The UK's leadership of the initiative will culminate in a major conference in London this October.
A tender has been launched to help with comms for the event, which will involve 1,500 delegates including heads of state, academics and major business figures.
The OGP was created in 2011 to secure commitments from governments on transparency and battling corruption. Chairing of the group changes annually.
With members across the globe, including the US, Brazil and South Africa, its efforts were recently bolstered by an agreement at last month's G8 conference.
The Open Data Charter, called 'a huge step forward' by the UK Government, saw G8 member countries endorsing a new drive to make information publicly available. However, both the UK and US governments have since come under fire for allegedly snooping on the public and foreign governments, following the leaking of information by former US security contractor Edward Snowden.
A Cabinet Office spokeswoman said that the UK's current presidency of the G8 presented the chance to make further progress on transparency at the OGP conference.
She said: 'It is an honour to be lead co-chair of the OGP, particularly in a year that has also seen transparency pushed to the top of the agenda as part of our G8 presidency.
'This summit will reflect our ambition to establish the OGP as pivotal in transforming societies around the world and the comms strategy will show how this ambition has moved from commitment to action over the past year.'
The six-month brief is understood to include on-the-ground comms support during the event at Queen Elizabeth II Conference Centre, which will also be attended by the world's media.