Maina Kiai, the UN special rapporteur on the rights to freedom of peaceful assembly and of association, said he was "appalled" to hear about the blacklisting of union members in the UK construction industry.
Speaking on a trip to London, he said: "It is crucial that strong actions be taken against the making and using of such lists as a deterrence."
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Georgia Jones, 18, and Tommy Cowan, 20, were named locally as the pair who died after being taken ill at the Portsmouth event.
Targets for recycled and recyclable packaging should also be brought in to encourage firms to ‘harvest’ waste from consumers.
The store’s customer service, value for money and standard of stores were criticised by shoppers.