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Updated at 1550 GMT

By Pranav Kashyap and Purvi Agarwal

May 23 (Reuters) -The UK's main stock indexes closed lower for a third consecutive session on Thursday amid political uncertainty ahead of UK's elections in July, while news of slowergrowth across businesses in May weighed on sentiment.

The blue-chip FTSE 100 index .FTSE and mid-cap FTSE 250 .FTMC each tumbled 0.4%.

A surprise call for a general election by Prime Minister Rishi Sunak spooked investors as they weighed the potential scenarios.

"Markets like certainty, and pre-election there is caution and a sort of political uncertainty that could weigh on demand for UK stocks and the pound," said Fiona Cincotta, senior market analyst at City Index.

Utilities shares .FTUB6510 fell 7.1%, leading declines among sectors,after energy infrastructure operator National Grid NG.L said it is looking to sell its Grain liquefied natural gas (LNG) terminal in Britain. The stock fell 10.9%, the biggest loss onthe FTSE 100.

Precious metal miners .FTNMX551030 weighed on the markers with a 1.7% slide, tracking lower prices of gold and silver. GOL/

On the brigher side, aerospace and defence sector .FTNMX502010 gained 2.4%, boosted by Qinetiq Group QQ.L after it hit a record high on an upgraded financial year outlook.

An upbeat quarterly earnings report from American chipmaker Nvidia NVDA.O boosted technology shares across global markets, liftingthe U.S. benchmark S&P 500 .SPX and tech-heavy Nasdaq .IXIC hit record highs.

A survey showed growth across British businesses had cooled more than any economist polled by Reuters had predicted.

Among stocks, Hargreaves Lansdown HRGV.L surged 14.4% after the investment platform rejected a 4.67 billion pound ($5.94 billion) takeover proposal.

Gains in Hargreaves supported the investment banking sector .FTNMX302020 to a more than two-year high.

Reporting by Pranav Kashyap and Purvi Agarwal in Bengaluru; Editing by Sohini Goswami, Krishna Chandra Eluri and Richard Chang

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