This weekend (1 July), at a parliamentary reception attended by the Indian president and prime minister, India's new Goods and Services Tax law was ushered in – marking a landmark in Narendra Modi's economic reforms.

India's complex state-level taxes and levies on goods and services were replaced overnight with one mechanism for trade between states and union territories.

This one move, the most radical than any Indian prime minister has made since the country's independence, will create a common market of 1.2 billion people – larger than the EU.

The rapid emergence of India has placed it at the top of the table of fast-growing major economies. India's relationship with the UK had been marked in recent years by a shift in the balance of power in India's favour.

India now needs transformational partners and global relationships. Will India wait for the UK to find its post-Brexit identity?

It is a vital question. We're standing on the brink of a renaissance in the UK's relationship with India. Soft power, influence, the rule of law, parliamentary democracy and even shared post-colonial history have been enough to support the special relationship, but now that relationship needs to stand on a different footing.

The UK's big ambition is securing a Free Trade Agreement (FTA) with India and making the most of its potential to boost trade and investment between the two nations. The City of London is already the leading centre of offshore rupee finance and India is the third-largest source of foreign direct investment in the UK.

Getting Brexit right and making the most of our transactional relationship is important, but to bring about a renaissance in UK-India relations, the UK should throw far more intellectual weight behind planning its future.

India and the UK have a chance to form a transformational relationship. The true value in this relationship lies in the power the UK and India have to change the world's course.

Among the greatest influences India and the UK could have in the world will include re-imagining the Commonwealth nations as a coordinated trading alliance to rival the EU, ASEAN and the proposed Regional Combined Economic Partnership (RCEP) – and trading initiatives to satisfy each nation's commitments to the 2016 Paris Climate pact.

In an astonishing reform of its energy infrastructure, India is predicted to exceed its renewable energy targets ahead of schedule. India's success in developing green infrastructure and supporting green capital flows could have greater influence in Europe and beyond – with the UK's help.

Innovation and creative collaboration on new ideas, ventures and technologies requires the free movement of ideas – in other words, the freedom of movement for travellers, tourists, students, researchers, business tourists and the labour force. The UK's political leaders' attempts to start this conversation have been clumsy.

We cannot rely on them to break the impasse. Over the next few years, the UK's government will be preoccupied with negotiating the terms of Britain's departure from the EU.

This will drain government resources – the civil service still has many vacancies in its Department for Exiting the EU, created nearly one year ago. And Indian diplomats openly say they are struggling to engage their counterparts wholesale in the Working Group that has been established to audit the trading relationship.

Prime Minister Theresa May visited India with her first international delegation last November, but any memories of the visit on India's part may be dim after she refused to make concessions on her arbitrary immigration policies, a vital condition to strengthening the bridge between the UK and India.

Short of radical overhaul of British visa and immigration policy – politically unthinkable in the UK's current climate – we need to activate diaspora communities, in particular, the highly successful Indian diaspora community, in the UK to build the strategies and structures to maintain overseas links.

This will take national-level campaigning, not unlike the party-political canvassing that peaks ahead of a general election, but involving people across the political spectrum – both Brexit and remainer.

Nonetheless, the UK's resistance to negotiating immigration terms belies a sinister suspicion of immigrants in the UK. The UK wants India's trade, but not its people.

Exposure to the benefits of the freedom of movement in different spheres of early life will lead to a gradual change in opinion for the younger generations who voted against Brexit and against the Conservative Party's Hard Brexit stance. In the long term, Britain will continue to be a European nation culturally, and will continue to thrive as a home of liberal democracy, creativity, innovation and forward thinking.

But the UK's reinvention as a sovereign power, open to the whole world, should be judged in part by how it takes this opportunity to transform the world through its partnership with India.

Manoj Ladwa is the founder of publisher India Inc and the editor of a new study of the UK and India's partnership, 'Winning Partnership: India-UK Relations Beyond Brexit'.