The announcement was made by British Secretary of State Peter Hain on Friday. He described the role of the consultative group as a forum for people to express their own views on how to address the violent legacy of the past.
Martti Ahtisaari together with South African lawyer Brian Currin will be invited as international advisors to offer advice on what lessons might be learnt for reconciliation in Northern Ireland from their wide-ranging diplomatic experience.
The former Finnish President is no stranger to the peace process in Northern Ireland. Earlier he served in a trio headed by Canadian General John de Chastelain which oversaw the first steps towards decommissioning of IRA arms following the signing of the Good Friday peace agreement in 1998.
Martti Ahtisaari, who celebrates his 70th birthday on Saturday, will continue to serve as U.N. Special Envoy to Kosovo.