"The India diaspora in the UK is one of the largest ethnic minority communities in the country equating to around 1.8 per cent of the population and contributing 6 per cent of the country's GDP," he said.
At an event at the British Parliament complex, he also described them as an "asset for building India-UK relations".
The event, jointly hosted by Indo-British All Party Parliamentary Group (APPG) and the APPG for the Commonwealth, was held to welcome Sarna to his UK posting earlier this year.
He briefed the Lords and MPs on major developments in India-UK ties, including the outcomes of the successful visit of Prime Minister Narendra Modi to the UK in November 2015.
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The High Commissioner urged the British parliamentarians to visit India to see first-hand and understand India in the larger context of the potential of the growing India-UK relations.
He also encouraged the audience to get more associated with the Nehru Centre, the cultural wing of the Indian High Commission in London, with a view to raising the level of intellectual activities of the centre.
Sarna's address was followed by an interactive session on varied topics that included visa issues for Indian students coming to the UK to study, Migration Advisory Committee's recommendations on Tier-2 Intra Company Transfer visas which are expected to hit Indian IT professionals and India's engagement with the Commonwealth.