The agency has been briefed to support the business as it continues its transition to a global multi-platform, multi-channel offering.

Activity will include the integration of features including text-giving, mobile views, smartphone apps and a full-service API.

The campaign will centre on a major piece of thought leadership, with the agency co-developing a data 'hub' and co-ordinating digital influencer outreach, a social media platform strategy as well conventional media relations.

The account will be led by Third City's co-founder Mark Lowe and the team will report to JustGiving's head of PR, Ros Holley.

JustGiving's head of marketing, Romain Bertand, said: "JustGiving is now more than 10 years old and we now have a huge range of tools and services to offer charities, businesses and consumers.

"As we look to grow the size and scope of the business, we've chosen to work with an agency with a strong data proposition. We’re looking to share our insights with a much wider audience and grow the world of giving even further."

Mark said: "JustGiving is one of Britain's major tech success stories and it’s fantastic that they are joining our growing portfolio of cutting-edge internet businesses."

JustGiving was founded in 2000 and has grown into the UK's most popular online fundraising business, raising more than £1 billion for more than 12,000 charities.