Now that the election has been called, Civil Servants are in what is referred to as "purdah" (also known as 'the pre-election period'). Guidance is issued by the Cabinet Office to all civil servants as to what is allowable. This year there are also local elections on 6th May, so employees of local authorities facing elections also jhave their own period of 'purdah'.An excellent Standard Note from the House of Commons Library is available here.
Should the result of the election be unclear, 'purdah' will continue until it is clear that a new government can command a majority in the House of Commons. This is usually when a vote of confidence has been held after the Queen's Speech.
