The British government is to formally apply to join a mammoth free-trade pact that includes Australia, Canada, Japan and New Zealand now that it has left the EU. Liz Truss, the international trade secretary, will ask to join the Comprehensive and Progressive Trans-Pacific Partnership (CPTPP) when she speaks to ministers in Japan and New Zealand on Monday. Negotiations are expected to start later this year, Truss’s department said, in announcing the move on the anniversary of the UK’s formal departure from the EU. Joining the CPTPP will cut tariffs in trading with its members. UK trade with the group last year was worth £111bn, according to the Department for International Trade. The pact’s 11 members are: Australia. Brunei. Canada. Chile. Japan. Malaysia. Mexico. New Zealand. Peru. Singapore. Vietnam. Boris Johnson said: “One year after our departure from the EU, we are forging new partnerships that will bring enormous economic benefits for the people of Britain. “Applying to be the first new country to join the CPTPP demonstrates our ambition to do business on the best terms with our friends and partners all over the world and be an enthusiastic champion of global free trade.” British businesses reacted warmly to the plans, with the Federation of Small Businesses (FSB) saying the move would help firms “thrive and succeed more than ever”. But the shadow international trade secretary, Emily Thornberry, said Labour will closely scrutinise any pact and called on the government to consult the public. “Like any other trade agreement, the advantages of joining the CPTPP will have to be assessed once we see the terms on offer,” she said. “At present, Liz Truss cannot even guarantee whether we would have the right to veto China’s proposed accession if we join the bloc first. “More generally, people will rightly ask why we have been through five years of debate in Britain over leaving a trade bloc with our closest neighbours only to rush into joining another one on the other side of the world without any meaningful public consultation at all.” Truss said joining the pact would “create enormous opportunities for UK businesses that simply weren’t there as part of the EU”. The Confederation of British Industry president, Lord Bilimoria, said: “Membership of the bloc has the potential to deliver new opportunities for UK business across different sectors.” Sue Davies – head of consumer protection and food policy at Which? – said ministers must ensure joining CPTPP “will bring clear consumer benefits” and will not dilute standards.