With the UK, the bloc will contain 590 million customers, 31 per cent more than the EU, according to Facts4EU.

The UK needed six of the 11 founding member countries of the trading bloc to ratify their previously signed agreement, in order for the UK to become the first non-founder member – although it only takes effect with regards to those countries that have ratified.

Peru made history on Thursday when the Peruvian Government ratified the accession of the UK to membership of the CPTPP.

It means the UK will embark on the largest trade deal in its history within the next three months, Facts4EU said.

The think-tank criticised the Labour Government for failing to announce the news on the UK Government website.

However, Secretary of State for Business and Trade Jonathan Reynolds celebrated the development in a newspaper article this weekend.

Writing for the Observer, he said: “It will mark a major milestone in our journey to full membership of a bloc that will boast a combined GDP of £12trn after the UK joins.”

He said the accession was a “real win for big-hitting British exporters”, but would also offer a boost for smaller businesses who are keen to break into these markets for the first time.

The CPTPP is a free trade agreement between 11 countries in the Asia-Pacific region: Australia, Brunei, Chile, Japan, Malaysia, Mexico, New Zealand, Peru, Singapore and Vietnam.

The six countries which have now ratified the deal are Japan, Singapore, Chile, New Zealand and Peru.

The remaining five, Australia, Brunei, Canada, Malaysia and Mexico, have signed the deal but are yet to ratify it formally, as a result of their parliamentary or other procedures.

The UK is the first non-founder member to be allowed to join, and 99 per cent of UK goods exports to CPTPP will be eligible for zero tariffs, Facts4EU said.

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The Dept for Business and Trade previously said: ”CPTPP is one of the largest free trade areas in the world… This Free Trade Agreement (FTA) spans the Asia-Pacific and the Americas and includes some of the world’s largest current and future economies.

“CPTPP will also provide the UK with a stepping stone to trade with the wider strategically important Indo-Pacific. It is expansionary at its heart.

“As new members join, the UK will be able to benefit from its expansion and increased opportunities to trade.”

Last year, former Prime Minister and former International Trade Secretary Liz Truss said: “As Trade Secretary, I made our formal application to join CPTPP two years ago. I am delighted negotiations are completed, deepening UK access to some of the world’s fastest-growing economies.

“This is Global Britain in action and an important counterweight to those who seek to undermine our values… This is a vital development as we seek to boost UK exports to new markets and deliver additional economic growth.”