Britain's medicines bill could jump by £100m a year if pharmacies are not able to source cheaper drugs from the Continent after Brexit.

Pharmacists currently buy the bulk of their medicines from UK wholesalers, but look to suppliers in mainland Europe for a minority to make savings.

Now the Healthcare Distribution Association (HDA), an organisation representing firms that supply 92pc of the NHS’s medicines, has warned that failure to agree a smooth exit from the EU could jeopardise patients.

Its members include giant Alliance Healthcare, the sister company of high street pharmacy chain Boots.

In a submission to MPs on the health select committee, which is gathering evidence on the potential impact of Brexit, the HDA warned it could lead to supply problems and health risks.

The HDA said that “disruption to the cross-border flow of medicines has the potential of placing patient safety at risk”. It warns a disorderly Brexit could lead to customs controls and added administrative hurdles slowing the supply of medicines to patients.