, which formed in 2000, specialises in search optimisation and brand positioning work for clients across the marketing sector and has clients in the UK, Germany, the US, France and Italy.
The business also provides brand monitoring, online PR consultancy work and copywriting for search engines, as well as brand consultancy services. It is understood Netrank will be integrated into LBi UK's existing search business.
Ewen Sturgeon, chief executive officer at LBi UK, said: "Netrank has impressed us with their ability to grow and evolve their revenues, services and client base consistently over the many years that we have worked alongside them for various clients.
"While both businesses stand to gain from the deal, we believe that our clients in particular will benefit enormously from our combined offering."
The acquisition follows the promotion earlier this month of Luke Taylor from UK chief to chief executive of the LBi Group, replacing Robert Pickering, who is to stay on the group's board.