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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Investigations into two MPs on both sides of the House are set to conclude - and both are proving tricky for their party leaders.
A trade union representative said the strike would either disrupt flights or generate substantial costs for the airline.
Joanne Adam needed a new liver, bowel, pancreas, and stomach, including her small and large intestine, after a rare tumour was discovered.