Those who were on leave were told the plans would already be under way by the time they returned, according to a senior civil servant familiar with the discussions.
Dave Penman, general secretary of the FDA union which represents senior civil servants, welcomed the changes to the structure of government but cautioned that relocation was a big decision for staff.
“Those considering a move out of London have the added concern that a return would be difficult given the disparity in house prices,” he said, adding a major consideration would be “whether it feels like a permanent reorganisation or something that could change quickly with a future government”.
Burnham has told cabinet members No 10 North is not a gimmick in a bid to reassure critics – and civil servants whose careers may be reshaped by the plan – who say it still has to prove it can make a lasting difference.
Dr Simon Kaye, author of the Re:State report told the BBC that No 10 North had to be big enough to outlast the Burnham administration.
“That means reaching a critical mass of people, establishing a genuine sense of shared purpose, and getting to a place where No 10 North feels different enough and vital enough that it can persist, no matter who the prime minister is,” he said.
While civil servants who spoke to the BBC largely welcomed the idea of a No 10 North, some doubted whether it would feel substantially different from existing regional government offices while the majority of ministers and political journalists, as well as many business leaders, continue to be based in London.
Some civil servants based in northern England believe they should have been given the opportunity to apply for jobs at No 10 North before discussions began about potentially lucrative relocation packages for staff moving from London.
One official, speaking anonymously due to the Civil Service Code, told the BBC: “I’ve built my career here and seen first-hand that the North is home to exceptional talent.
“No 10 North needs to make the best use of all talent and create opportunities for people to build careers close to the communities they serve.”
Northern Powerhouse Partnership chief executive Henri Murison said the government had been moving civil servants out of London for several years, including to the new Darlington Economic Campus, adding: “This has seen a number of senior civil servants be based from here but only rarely ministers.”