The site, which was sold by co-founder Arianna Huffington to AOL earlier this year, handed MBA the business following a pitch against three other agencies. MBA will oversee online and offline communications for the launch, as well as planning.
AOL acquired The Huffington Post, which has around 25 million monthly users, for $315 million (£195 million) in February.
The new version of the site will focus on UK content, but will also link to material on the US portal. It will follow the same model as the US version, which employs a core team of writers and editors while also sourcing material from unpaid bloggers.
Since the acquisition, AOL has axed around 900 editorial staff, around 20 per cent of its workforce, as it restructures to integrate The Huffington Post with its other websites.