Warning by European Medicines Agency reinforces logistical concerns about Brexit.

The head of the EU’s London-based drugs regulator said the agency had lost an unprecedented number of senior staff since the Brexit vote and warned that as many as half could walk out unless its future is handled properly.

For Guido Rasi, executive director of the European Medicines Agency, its probable relocation once Britain leaves the EU poses a unique challenge but is also a stark reminder of the broader administrative and logistical quagmire that is likely to follow Brexit. The EMA’s Canary Wharf headquarters plays host to 36,000 national regulators and scientists each year from across the continent who come to London to approve the safety and efficacy of drugs for the EU’s 500m people. London’s 890-strong secretariat plays a central role in coordinating that work. Prof Rasi said seven senior executives had quit the agency since the referendum, more than in the past decade put together. A staff survey presented to the agency’s governing board last week showed that about 50 per cent would leave in the event of relocation to an undesirable city.