The new Strikes (Minimum Service Levels) Bill gives the Government the power to ensure unions provide essential cover
The union said its members in 124 government departments and other bodies will walk out on February 1.
More than 21 gigawatts of wind power was being produced early on Tuesday evening.
Lawyers from several UK firms have said that employers are unlikely to want to sack their workers over breach of the proposed law.
Paramedics, emergency care assistants, call handlers and other staff will stage a major walkout on Wednesday.
Thousands of members of the Transport Salaried Staffs’ Association in Network Rail will strike.
Shares rose in London after a rollercoaster day.
The influential S&P Global/ CIPS flash UK composite purchasing managers index showed a reading of 47.2 in October, below September’s 49.1.
Rishi Sunak or Penny Mordaunt will face an in-tray piled high with problems.
Both the FTSE 100 and the pound gained on Monday, while the cost of Government borrowing fell.