Britain will tell Brussels it is prepared to stay tied to the customs union beyond 2021 as ministers remain deadlocked over a future deal with the EU, the Telegraph has learned.

The Prime Minister's Brexit war Cabinet earlier this week agreed on a new "backstop" as a last resort to avoid a hard Irish border, having rejected earlier proposals from the European Union.

Ministers signed off the plans on Tuesday despite objections from Boris Johnson, the Foreign Secretary, and Michael Gove, the Environment Secretary. A pro-European Cabinet source said that Mr Johnson and Mr Gove were "outgunned" during the meeting and reluctantly accepted the plans.

The Brexit sub-committee reached a consensus that Britain will stay aligned to the customs union if highly complex technology needed to operate borders after Brexit is not ready. Officials have warned it may not be in place until 2023.

Sources said that the new Irish "backstop" will be strictly "time-limited" and make clear that Britain will be free to implement trade deals.