Up to 1,500 jobs are to be axed by the Land Registry and five offices will close under cost-cutting plans.
Union leaders condemned the announcement, which they said had "shocked" workers.
Offices in Peterborough, Portsmouth, Croydon, Stevenage and Tunbridge Wells will close and other changes will affect staff in Plymouth and London.
The Public and Commercial Services Union said 1,100 jobs will be lost by the office closures and a further 400 staff face having their jobs privatised.
Almost one in five workers at the organisation in England and Wales will be affected by the announcement, said the Public and Commercial Services Union.
Mark Serwotka, the union's general secretary, said: "Staff are shocked and angry about these plans.
"With 1,700 jobs already gone, there is a real danger that services to the public will suffer as the agency is cut to the bone.
"Added to job cuts and office closures, staff have the double whammy of privatisation hanging over their heads.
"Experience shows that privatisation isn't the silver bullet to save costs and often provides poor value to the taxpayer with corners cut in a bid to turn in a profit.
"The Government needs to recognise that putting hardworking civil and public servants on the dole at a time of economic uncertainty will only prolong the recession and the communities affected."
