By bizn_fun 
A customs union would eliminate tariffs or taxes on some or all goods between the UK and the EU, reducing bureaucracy.
But critics point out that it would also severely curtail the UK’s ability to strike bespoke global trade deals, as the EU would place a common tariff on all goods from outside the customs union area and would expect the UK to conform to common standards.
Labour’s election manifesto ruled out signing up to the existing EU customs union.
The party also said it would not rejoin the EU’s single market, where countries adopt common laws in some areas to make it easier to trade goods and services.
Calls for a customs union with the EU have been growing among Labour MPs, while Justice Secretary David Lammy said one could boost economic growth.
Asked by the BBC whether Brussels would welcome talks on Britain rejoining the customs union, Dombrovskis said: “I cannot jump to conclusions, but I can say that we are ready to engage with an open mind and seek those areas of cooperation.”
He said it was unlikely Britain will return to the single market, stressing that access would require the UK accepting freedom of movement.
The single market relies on a country accepting “the four freedoms”: freedom of movement, goods, services and capital.