LMG will continue to target customers individually with personalised vouchers based on how they use their Nectar cards, but Unica's software will enhance the efficiency and effectiveness of the communications that LMG sends out, the group said.
The software will enable LMG to increase the number, type and complexity of its direct marketing offers, which are delivered via email and direct mail, to its collector base comprising around 50% of UK households.
Simon Hawkes, chief operating officer at LMG, said: "With an ever-growing customer base, Unica will help us to respond to demand more quickly and enable us to develop more targeted marketing campaigns and offers.
"It will also help to free up our campaign team to focus on ensuring the campaigns deliver what our customers want."
LMG will also use the software for its new insight and communications business.
LMG's Nectar customer loyalty programme allows customers to collect and redeem points at 6,000 retail outlets across the UK.
Nectar's partners include Sainsbury's, which renewed its Nectar contract in March, Gala Bingo, Debenhams and Argos.