Brexit plan to leave customs union not ready until 2021: tax chief

A post-Brexit blueprint to replace Britain's customs union with the European Union will not be ready until the end of 2020, tax chief Jon Thompson has told lawmakers.

The "maximum facilitation" proposal favoured by Brexit supporters, which would use trusted-trader arrangements and technology to avoid border checks, could take three years to fully implement, HMRC chief Jon Thompson told the Brexit Select Committee, its chairman said Wednesday.

Britain has vowed to leave the EU's single market and customs union after Brexit, which legally takes place on March 29, 2019, but the real exit date will in effect be delayed by a transition period lasting until December 31, 2021.

Chairman of the committee Hilary Benn revealed Thompson had written to lawmakers saying that parts of the so-called "max fac" plan "could take around three years, which takes us beyond December 2020".

The "max fac" is favoured by leading Conservative Brexiteers Boris Johnson and Michael Gove, but Prime Minister Theresa May is believed to support a new "customs partnership".

Under this arrangement, Britain would collect tariffs on behalf of the EU for goods heading to the continent.

Foreign Secretary Johnson on Wednesday urged May "to get on with" plans to leave the customs union, so that Britain can be free to strike trade deals with the rest of the world.