Millions of Britons will have to pay €7 (£6.29) every three years for visa-free travel to the EU from 2021.

The post-Brexit move was confirmed by the European Commission in response to a question to its President Jean Claude-Juncker.

Alongside the fee, UK citizens will need to pre-register for the three-year electronic visa waiver.

The small print of the detailed draft regulation covering visa exemptions for UK citizens travelling to the bloc says that "the European Travel Information and Authorisation System (ETIAS) will apply to United Kingdom nationals once union law on free movement of union citizens ceases to apply to them, as to other visa-free third country nationals".

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The maintenance of visa-free travel for short-term visits to the EU, and by all EU citizens to the UK has been heralded by the government and Prime Minister Theresa May as one of the great achievements of the political declaration agreed by EU leaders at the special summit last month.

In an interview with Sky News at the recent G20 summit in Argentina, the PM was asked whether if the public wanted to avoid the imposition of this charge MPs would have to vote down her deal.

Mrs May said at the time: "You're talking about what might be an implication of leaving the European Union, I am talking about having negotiated a deal that ensures that we can maintain the good relationship that are good for our citizens across a whole range of areas, it means we are not a member of the EU so we can do our own trade deals around the world, we can end free movement once and for all."

The EU has already begun to implement the system which preauthorises the entry of citizens from a special list of countries, who do not require full visas.

"Once ETIAS enters into operation, all visa-exempt non-EU nationals who plan to travel to the Schengen area will have to apply via ETIAS," a European Commission source told Sky News.

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There had been some hopes privately in government and publicly from Conservative Brexit supporting MPs that the UK could negotiate an exemption from the new US-style preregistration and payment requirement.

Previous suggestions that this scheme would apply had been dismissed as "Project Fear" by Brexiters.

The change would not have applied if the UK had remained in the EU, and also might be put off if the transition period is extended and EU laws on freedom of movement continue to apply to the UK.