Alistair Darling, the work and pensions secretary, said that 225 of the new offices would open within the next year. Some 750 staff have been on strike in the 56 existing offices in protest at the removal of security screens.
Mark Serwotka, general secretary-elect of the PCS union, said 10,000 staff would join the strike if the government refuses to re-introduce secu rity screens in the new offices.
The union is demanding that each of the new offices contains a small screened area for staff to deal with difficult cases.
The new offices are designed to encourage people back into work by placing advice about jobs and benefits in one place.