The Government said it was "disappointing" that the PCS union is planning three months of industrial action, including a huge strike on Budget day.
A Cabinet Office spokesman said: "It is disappointing that, yet again, the PCS insist on pushing for futile action which benefits no-one, and damages the services they deliver to the public."
More top news
Last minute preparations are going on at the Church of St Mary Magdalene where Princess Charlotte will be christened.
Princess Charlotte is being christened on Sunday at Sandringham in Norfolk in only her second public appearance since she was born.
Thunderstorms clear the North, leaving a dry and warm day with sunny spells.