In a letter to staff, chief executive David Pemsel and editor-in-chief Katharine Viner said that "operating costs remain too high, trading conditions remain tough, and further changes and cost savings will be necessary" as the business seeks to break even by 2018/19, The Telegraph reports.
GMG will give each department a cost saving target that must be met through a combination of job cuts, reduced expenses and other costs.
Pemsel and Viner added: "Our three-year plan is a response to seismic changes in our industry, not least the shift of new and existing print and digital advertising revenues towards Google and Facebook."
GMG has so far focused on voluntary redundancies, with 250 staff leaving last year. It has also sought to grow revenues through its memberships scheme, which was launched in 2014 and hit 200,000 members earlier this month. The paper is aiming for this figure to reach one million by 2018/19.
On Monday, Pemsel revealed at Advertising Week Europe that GMG had invested in a mobile video advertising start-up called Vidsy through investment fund Guardian Ventures.