Big Society Capital, which was launched by Prime Minister David Cameron in April with £600m of funds to invest, has hired Newgate Communications to help underpin its comms efforts.
The organisation was created by the Government to be the cornerstone investor in and driver of the UK's emerging social investment market.
Newgate has been called in to support the bank's business strategy and help communicate the creation and development of the social investment market itself.
Alastair Ballantyne, head of comms for Big Society Capital, said: 'Big Society Capital is developing a strong, diverse and sustainable social investment market in the UK.
'Our challenge is to reach out and influence a diverse range of stakeholders, from social and charitable organisations to local government and financial audiences.'
It is understood that the brief calls for Newgate to help bring these diverse market participants together and educate them on the benefits of the social investment market and Big Society Capital's central role underpinning it.
In particular, it is thought that Big Society Capital is looking to attract a wider spectrum of investors.
The account will be led by Newgate directors Jason Nisse and Andrew Robinson.
Nisse commented: 'Social investment brings together the social sector and financial markets, unites left and right and, with Big Society Capital leading the way, has the potential to bring positive change to many people’s lives.'
Big Society Capital previously retained HB Communications, but earlier this month held a competitive pitch involving several large corporate PR specialists for an expanded brief.
Big Society Capital is part of a wider Government drive to entice UK business and financial communities to help tackle social issues.
Last week, the Government unveiled two new social impact bonds worth up to £8m, which will enable Thames Reach and St Mungo's to combat homelessness in London.