The London-headquartered print group has agreed to invest £1.5 million in cash in the form of convertible loan stock, which is the equivalent to a 24% equity stake in the £2.7m turnover business.

It will also have the right of first refusal in the event of the sale of all or part of the remaining equity in the business, which remains majority-owned by its co-founders.

Following the investment, the two companies will work together going forward, but Sponge will continue to be managed by its existing management team from its current premises, with minimal interference from its new parent.

A statement from St Ives said: "The investment in Sponge represents a further step in St Ives' strategy to create a complementary range of digital and marketing services that will enable the group to add value to existing and new clients."

Established in London in 2002, 22-staff Sponge provides mobile marketing solutions and mobile services to a number of leading global brands, including Adidas, Coca Cola and McDonalds.

The company recorded pre-tax profit of £79,078 in 2010 and £96,799 in 2009, when its turnover was £2.8m.

In the past year, St Ives has made a number of moves to complement its print business. Most recently it acquired Marketing Planning in February, while last September it made two purchases in a week, buying Response One and Pragma Holdings. Last February, it also took a 90% stake in Tactical Solutions.