The UK‑US trade agreement had reduced the company’s export tariff from 27.5 per cent to 10 per cent, but those gains are now at risk.

Pharmaceutical manufacturers could face even greater exposure.

The sector is valued at £17.6billion a year and accounts for around 17 per cent of UK business research and development spending.

Medicines had previously been fully exempt from US tariffs.

Mr Trump has warned the situation could escalate further.

Tariffs are set to rise to 25 per cent on June 1 unless Denmark agrees to sell Greenland.