The generic drug industry has warned that US tariffs on pharmaceuticals risk causing shortages of medicines including cancer treatments, and that manufacturers might stop making products that become unprofitable as a result.

Generic medicines, which are cheaper versions of drugs that no longer have patent protection, make up about 90 per cent of US drug supply. The majority are manufactured outside the US, in lower-cost countries such as India. The active ingredients used in the products often come from China.

So far, pharmaceuticals have avoided the wide-ranging new US tariffs. But President Donald Trump has repeatedly said he plans to apply them to the sector, and the US commerce department this week has said it is investigating the national security implications of pharmaceutical imports.