Firms 'face deluge of paperwork if UK quits customs union'
Businesses face being deluged with 60 million more pieces of paperwork every year if Britain quits the customs union, according to campaigners.
Membership cuts out much of the bureaucracy around exports and imports but a so-called hard Brexit would leave firms with waves of extra documentation, according to the pro-single market Open Britain.
It used World Customs Organisation figures from last year showing the UK made 70.5 million import declarations and 6.5 million export declarations for non-EU goods trade to predict a similar ratio would be needed for trade with the EU.
New forms would be needed for around 45 million import declarations and 15 million export declarations, Open Britain estimated.
Members of the customs union - which covers not only the 28 EU states, but also Turkey, Monaco, San Marino, Andorra and non-EU UK territories such as the Channel Islands - enjoy free trade with one another but must impose the same tariffs on goods arriving from outside the area, and are barred from doing bilateral trade deals with other countries.
Labour former shadow chancellor Chris Leslie said: " Brexit isn't a liberation from red tape but the beginning of an avalanche of paperwork for businesses trading with Europe.
"Ministers should commit to publishing a full cost-benefit analysis of the consequences of leaving the customs union, rather than just airily asserting that it will benefit our trade and our economy without any evidence for those claims."
It comes as a think tank instructed lawyers to begin a legal challenge over whether leaving the EU means automatic withdrawal from the single market.
British Influence wants a judicial review of the Government's legal position on membership of the wider European Economic Area which forms the internal trading bloc.
It believes leaving the EU does not mean quitting the EEA which extends the single market's tariff-free trade in goods to countries like Norway, Iceland and Liechtenstein.
A legal challenge could result in Parliament being given the final say on EEA membership.
A spokesman said: "There is no need for a hard Brexit and there is no mandate for a hard Brexit."