The six-month operation targeted internet users who access child abuse images but has already led to charges for serious sexual assault.
Among the several hundred people arrested across England, Wales, Scotland and Northern Ireland are workers who had access to children through their jobs and had no previous contact with police.
The massive investigation, involving 45 police forces, led to hundreds of children being "safeguarded", the NCA said.
It stressed that none of those arrested is a serving or former MP or member of the Government.
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The PM faces a countdown to settle a deal before her minority government tries to get its Queen's Speech plans approved by the Commons.
More details will come today on proposals to offer EU residents the right to a new "settled status" in Britain after it leaves the bloc.
Scotland and Northern Ireland could see rain later but for the rest of the UK it should be a fine day.