GN&M told employees that it was looking to shrink staff numbers in the editorial department from 850 to 800 as part of a plan to reduce editorial costs by £10m.
The publisher hopes to meet the reduction by continuing its voluntary redundancy scheme, freezing current vacancies, and by not replacing departing staff.
Management said in an email to staff: "These changes aren't just short-term measures to get us through this current financial downturn.
"They are also about preparing us for journalism in the 21st century, and helping to preserve GNM's journalism in what is a declining newspaper market and a time of great change and challenge for the media industry in general."
Guardian Media Group, parent company of GN&M, imposed an across the board pay freeze for 2009 in February in anticipation of a difficult year.
The pay freeze was said to apply to GMG's wholly owned businesses, which include Guardian.co.uk, MediaGuardian.co.uk, the Manchester Evening News and GMG Radio.
The Guardian and the Observer are the last two national titles to announce staff cuts or redundancies since the economic downturn began.
News International announced in February that it was cutting 65 editorial jobs across its four national titles, the Sunday Times, The Times, The Sun and the News of the World, as part of an efficiency drive.
In January, the Financial Times said that it planned to make up to 80 staff redundant across several departments, while IN&M reported last November that 90 jobs, about 60 of them editorial, would be cut from its national newspaper division in the UK to save £10m.
The Telegraph Media Group also announced last November that it planned to reduce its editorial staff by 10%, a move that was set to put about 50 journalists out of work.
