Mexico City - When George Clooney and his two partners sold their upscale Casamigos tequila to the UK-based drinks group Diageo six months ago, the $1bn valuation caused eyes to water. Now Bacardi has raised its own toast to the increasing popularity of the high-end tequila market.

The world's largest privately held spirits company, owner of the eponymous rum as well as Grey Goose vodka and Bombay Sapphire gin, has agreed to buy full control of Patrón Spirits International in a deal that values the world's top-selling ultra-premium tequila at a whopping $5.1bn.

Bacardi owns more than 200 spirits brands and Patrón joins a portfolio which includes the Cazadores and Corzo premium tequila labels.

Tequila and mescal, the agave-based Mexican spirits once synonymous with shots, slamming and brutal hangovers, have carved a fast-growing niche at the luxury end of the spirits market. While tequila sales overall grew 5.3 per cent in 2016 from 2015, ultra-premium tequila and mezcal sales surged 35 per cent in the same period, according to the IWSR, the London-based authority on the drinks industry.

Bacardi said it was not releasing the financial details of the transaction, which boosts its stake in Patrón from 30 to 100% and is expected to close in the first half of this year.

Patrón, founded in 1989 by US entrepreneurs John Paul DeJoria and Martin Crowley, is a top-seller in the fast-growing spirit segment. It had sales of $1.6bn in 2016, according to consultancy Euromonitor, after their value grew 7 per cent from 2011 on a 5.1 per cent increase in volumes.