London transport workers has been warned of razor blades being hidden behind posters promoting Covid conspiracy theories.

       Transport for London (TfL) said it had advised its staff on how to safely remove unauthorised posters put up on its network following a a number of reports of concealed blades.

       It said its staff act urgently to remove all prohibited material including those with anti-vaccination sentiments or misinformation.

       A spokesperson said: “The safety of our customers and colleagues is paramount, and we have issued guidance to our staff on how to remove them safely after reports of instances outside of our network of razor blades being attached to the back of such materials.

       “None have been detected on our network and there have been very few instances of unauthorised adverts related to the pandemic.”

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       A bulletin sent by TfL warned staff of “propaganda posters” pushing conspiracy theories and misinformation about Covid and vaccines had been placed on doors, lampposts and walls, The Guardian reported.

       The message was accompanied by two pictures: one of a poster which read “masks don’t work”, and another showing its reverse splattered with blood held by someone carrying a bloodied tissue.

       They appeared to be related to an incident in July in which a woman in Wales was injured by a razor blade glued to the back of a poster promoting Covid untruths.

       Trade union RMT condemned the “disgusting practice” and called for the perpetrators to face criminal action.

       General secretary Mike Lynch said: “Any anti-vax conspiracy theorist resorting to this disgusting practice of lacing their propaganda with razor blades needs to know that they will face criminal prosecution and the highest possible sentences.”