Unions and business leaders welcomed Jeremy Corbyn's speech on Brexit, although directors say there are still unanswered questions.
Unite general secretary Len McCluskey said: "Jeremy Corbyn has shown that people really do have a choice on Brexit.
"On the one hand, there is Labour which has pledged to build on the trading arrangements presently supporting millions of jobs in this country.
"A Corbyn government will also make it a priority to tackle the greedy bosses who have abused migrant workers to undermine employment conditions and attack the rate for the job.
"On the other hand, there are the Tories who are quite clearly putting their own party interests above those of the nation."
Paul Everitt, chief executive of ADS, the trade association for the aerospace, defence, security and space sectors, said: "A customs union with the EU is a practical solution that would put businesses in the best possible position to compete after Brexit.
"We welcome the position set out by the Leader of the Opposition today that Labour will support a customs union with the EU and stay in important EU agencies."
Stephen Martin, director general of the Institute of Directors, said: "While Labour has firmed up their position on customs today, there are still many unanswered questions from both Labour and the Conservatives about the UK's future relationship with EU, and this is making it hard for businesses to plan.
"As with everything about the Brexit process, extracting detailed and specific answers on the future trade arrangements from our political leaders has been a slow and laborious process."
Tim Roache, general secretary of the GMB union, said: "The Government's approach to Brexit would have a negative impact on many industries where our members work.
"By committing to a customs union, Labour is showing clear leadership that would safeguard our ports, transport firms and manufacturing sectors."
Ian Wright, director general of the Food and Drink Federation, said: "The Leader of the Opposition is correct to highlight the complexities of those supply chains which rely upon on barrier-free and tariff-free trade.
"The success of UK food and drink manufacturers depends upon the frictionless movement of ingredients and finished products - nowhere is this more stark than on the island of Ireland, where food and drink can cross the border five or six times."
Transport Salaried Staffs' Association general secretary Manuel Cortes said: "TSSA welcomes Jeremy's approach that places the people of Britain rather than the Tories back at the heart of the Brexit conundrum.
"Jeremy is right that we are all in this together. He is the only politician people now trust to deliver a Brexit approach that will be in the interests of the many not the few."
Carolyn Fairbairn, director general of the CBI, said: "The Labour leader's commitment to a customs union will put jobs and living standards first by remaining in a close economic relationship with the EU.
"It will help grow trade without accepting freedom of movement or payments to the EU.
"Importantly, a customs union will go part of the way to providing a real-world solution to the Irish border question that is of such urgent concern to the people and firms of Northern Ireland.
"But businesses have their eyes wide open on Labour's overall rhetoric on re-nationalisation.
"If Labour turns its back on good collaboration between the Government and the private sector - putting vital sectors solely in the hands of politicians - public services, infrastructure and taxpayers will ultimately pay the price.
"The CBI will continue to engage with the Labour Party to find better solutions to the shared challenges we face."
TUC general secretary Frances O'Grady said: "The Labour leader's speech was a welcome step forwards.
"It provided some of the answers working people need on how their jobs, rights and livelihoods will be protected, and it exposed the threat to manufacturing jobs from the Government's red line on a customs union."