Oxfam GB is expected to cut more than 200 jobs in a bid to make savings of about £16m a year.
The charity, which employs slightly more than 2,000 people in the UK, said it had begun talking to staff about the planned changes, which would help it to fulfil its strategy over the next 10 years.
It said it hoped to avoid redundancies “wherever possible”.
Major changes put forward by the charity include merging its campaigning and international programme support to create a new “integrated impact division” that will address some of the world’s most pressing drivers of poverty and inequality, the charity said.
It said the new division would focus on protecting the poorest and most vulnerable communities during the coronavirus pandemic and from climate change, and work to break down the barriers that prevented millions of women around the world from earning a decent living.
The charity said it also planned to create a new supporter engagement division that would promote a more joined-up approach to supporter activities.
An Oxfam spokesman said that because this was a consultation he was unable to say where the bulk of any job cuts might come.
The consultation will last for three weeks and the charity expects to make final decisions about structural changes next month.
The consultation on the changes was due to begin in March but was delayed and amended because of the impact of the coronavirus outbreak.
The news comes after Oxfam International, which operates in 66 countries and has 20 affiliate members, including Oxfam GB, announced last month that it planned to cut almost 1,500 jobs and withdraw from 18 countries as part of a major restructure.
Oxfam GB, which plans to begin reopening its network of stores in England on 15 June, said the closure of its shops and the cancellation of fundraising events because of the Covid-19 outbreak was costing it about £5m a month.
It said recent exceptional legacy income had helped it to weather the economic impact of the pandemic while expanding its work to protect communities from the coronavirus by providing clean water, sanitation and public health promotion activities.
Danny Sriskandarajah, chief executive of Oxfam GB, said: “These strategic changes are long planned, but I am sorry to be adding to the concerns of our dedicated and talented staff during this difficult time.
“The financial reality – not least the ongoing and uncertain impact of Covid-19 – requires us to act now to ensure we live within our means. We will continue to consult fully and fairly with staff and their union representatives in reaching a final decision.”
He said the charity would focus its efforts on “delivering transformative programming in fewer places and on fewer issues so that we concentrate resources and maximise the difference we make”.
Sriskandarajah added: “And we are transforming ourselves into a more agile and globally balanced network of individuals, communities and organisations, committed to tackling the common challenges that face people living in poverty around the world.”