Up to 200 staff at Christian Aid are at risk of redundancy after the charity made the "difficult decision" to withdraw from 12 countries as part of plans to save £7m a year.
The anti-poverty charity said its new global strategy, called Standing Together, would enable it to have a bigger impact in the communities within it worked.
In a statement, the charity said it was "mindful of the external challenges facing the charity during a period of political uncertainty and a tough environment for unrestricted fundraising".
It said it aimed to reduce its unrestricted spending from £47m to £40m a year over the next 12 months.
"This will, unfortunately, require that up to 200 staff are at risk of redundancy, in a process that will begin with a formal consultation by early October," it said.
About half of the jobs at risk are in the UK, giving rise to about £3m in savings, with the remaining £4m being saved outside the UK.
Christian Aid recorded an income of £117.9m and expenditure of £111.1m in the year to the end of March 2018, its latest accounts show. It employs about 1,100 people.
The charity’s statement said the new strategy would enable it to be "more focused and deepen its interventions in fewer countries and to do so as good stewards living within our means".
It will retain its programmes in 15 countries.
Amanda Mukwashi, chief executive of Christian Aid, said: "After careful consideration of every piece of work Christian Aid does, the senior leadership and trustees have made the difficult decision to exit from some countries and instead, in some cases, work regionally to have greater impact.
"The decisions have been tested against the new strategy and global poverty, vulnerabilities and inequality indices."
She said the charity would start the process of exiting its programmes in Angola, Egypt, Zambia, Mali, South Africa, Ghana, the Philippines, Nepal, Bolivia, Colombia, Guatemala and El Salvador.
The charity’s work in Latin America will be managed as a regional programme from Brazil and its work in the Middle East will be run as a regional programme from London.
"A process of consultation with staff will be started to establish the best way of managing each transition and staff in each of the countries where our presence will be changing," said Mukwashi.
She said the charity’s transition plan was based on it planning to do "a few key things well, supported by systems and structures that are streamlined and efficient".
She said the strategy required the charity to "focus our work so that every programme reflects our commitment to the very poorest, speaking truth to power and working, as we always have, with and through very local organisations".
Mukwashi added: "This will help to amplify the voice and agency of local partners and ensure long-lasting resilient communities able to stand in the face of multiple challenges."