No-deal contingency plans to safeguard medicine imports are set to be triggered on Wednesday, despite the potential delay to Brexit, with approved suppliers told to book space on the government’s emergency ferry service.

Although the prime minister is to request an extension to article 50 which would postpone Britain’s departure from the EU, Whitehall will enact plans to ensure the flow of critical supplies should Dover be gridlocked after 29 March.

The Department for Health, the Department for Business, Energy and Industrial Strategy and the Department for Environment, Food and Rural Affairs will tell companies who have registered to import “category 1” goods for the NHS and farming to start purchasing tickets from the operators of the special Channel crossings, which were controversially procured by the Department for Transport at the end of last year.

Part of the initial £103m contract with three operators fell through after Seaborne Freight was revealed to have no ships, while the government was forced to pay Eurotunnel £33m after it sued over the secretive procurement process.

Additional routes from France to the south coast ports of Plymouth, Poole and Portsmouth will be run by Brittany Ferries from 29 March, while DFDS Seaways will operate extra crossings to Felixstowe in Suffolk and Immingham in Lincolnshire from the Netherlands and Germany.

Last August, the health secretary wrote to firms that supply pharmaceuticals to the NHS to ask them to stockpile six weeks’ worth of goods in the UK ahead of Brexit and to look into airlifting items with a short shelf life.

The government has since set up a logistics hub in Belgium to stockpile vital medical products for the NHS, from which trucks will come to the UK via ferry crossings of up to 16 hours.

Stents, implants and other products needed to ensure that patient care is not disrupted will be stored at the hub, the exact location of which has not been disclosed.

A government spokesman said: “Leaving with a deal is still our priority, but as a responsible government it is only right that we push on with contingency measures. We have secured additional freight capacity to ensure critical goods such as medicines can continue to enter the UK in the event of a no deal and are engaging with suppliers on the process for sales.”