The organisation said despite early signs of promise the current evidence shows it does not improve survival or reduce the need for mechanical ventilation as well as being costly and time-consuming to administer.
The WHO said it had made “a strong recommendation” against its use in patients with non-severe illness and a recommendation against its use in patients with severe and critical illness.
Its recommendations are based on evidence from 16 trials involving 16,236 patients with non-severe, severe, and critical covid-19 infection.
It comes as Health Secretary Sajid Javid confirmed the Omicron variant of coronavirus is now circulating within the community.
Mr Javid told MPs on Monday “multiple regions of England” were seeing cases of the variant not linked to international travel.
And he said he could not guarantee the variant would not “knock us off our road to recovery”, as he said the “the window between infection and infectiousness may be shorter for the Omicron”.
Earlier, Professor Paul Hunter, from the school of medicine at the University of East Anglia, had warned the Omicron variant could be spreading faster than a previous variant, Delta.
He told BBC Breakfast: “How it’s likely to spread in the UK still uncertain, but I think the early signs are that it will probably spread quite quickly and probably start outcompeting Delta and become the dominant variant probably within the next weeks or a month or so at least.
“The big remaining question is actually how harmful it is if you do get Covid with this Omicron variant, and that’s the question that we’re struggling to answer at the moment.”
Mr Javid told the Commons there were now 261 confirmed Omicron cases in England, 71 in Scotland, and four in Wales.
But he said that as far as he was aware, none of the 336 people with a confirmed case of Omicron in the UK had been admitted to hospital.