Sir Keir Starmer told Indian counterpart Narendra Modi the signing of a trade deal was a “historic day” for the two countries.
At the Prime Minister’s country residence Chequers, Sir Keir said the deal marked a “step change” in relations.
Mr Modi said they were “writing a new chapter” in the UK and India’s shared history.
The deal is set to be worth £6 billion in investment for the British economy and the two leaders have also agreed to increase efforts to tackle illegal migration and organised crime.
Sir Keir said: “I’m really pleased and privileged to welcome you here today on what I consider to be a historic day for both of our countries, and the delivery of the commitment that we made to each other.”
Mr Modi, speaking via a translator, described the UK and India as “natural partners”.
Business Secretary Jonathan Reynolds and his Indian counterpart Piyush Goyal then formally signed the trade agreement in the great hall of Chequers.
