Britons visiting the EU could be slapped with millions of pounds in surprise credit and debit card charges in the event of a no-deal Brexit, the UK Government has warned.

A technical paper released on Thursday laid bare the risks facing UK banking and payments customers if the Government fails to clinch a trade agreement that covers financial services.

In the case of a no-deal Brexit, UK-based payment service providers would lose direct access to the EU's payment infrastructure.

Customers, including businesses using providers to process payments in euros, could also "face increased costs and slower processing times for euro transactions", the government paper warned.

"The cost of card payments between the UK and EU will likely increase, and these cross-border payments will no longer be covered by the surcharging ban," it added.

The ban prevents businesses from charging customers for paying by the likes of PayPal or debit or credit cards, which Treasury earlier this year characterised as "rip-off fees".

Consumers shopping in the EU or buying online from an EU company with a UK card, could be hit with surprise charges on their purchases, with some retailers charging more than the cost of processing payments.

The Treasury estimated that surcharging cost Britons around £166m in 2015.

The EU surcharge ban came into force in January.

The Government said it is looking to align domestic law around payments with rules already set up in the EU in hopes of remaining a member of the Single Euro Payments Area.

However, that would only ensure that "lower value euro transactions are processed in the same amount of time as they are today", meaning larger payments may still face delays.

New medicines will need UK approval before they can be made available to patients in the event of a no-deal Brexit.

The Medicines and Healthcare products Regulatory Agency (MHRA), which regulates drugs in the UK, will take on the functions of the EU if an agreement is not reached by March 29.

Products will have to go through national assessment before they receive market authorisation to be sold in the UK, according to a technical paper on no-deal Brexit preparations.

The notice states: "After EU exit, to market a product in the UK, an initial market authorisation application will need to be submitted to the MHRA and will go through a national assessment.

"MHRA will take a streamlined approach to approving UK market authorisation applications that places no greater burden on industry and ensures that patients can access new and innovative medicines at the same time as EU patients."

Most new medicines currently come to the market through a licensing route overseen by the European Medicines Agency (EMA).

However, if a deal is not reached, the UK's current participation in the European regulatory network including centralised routes will cease, according to the guidance.