Both Corona Extra and Red Stripe are to leave the Wells & Young's portfolio next year.
The brewer has had a deal to distribute Corona Extra for 15 years and Red Stripe for 30 years but when the two deals come to an end in 2011 they will return to Grupo Modelo and Diageo respectively.
The Mexican Grupo Modelo has yet to say what it plans to do with Corona following the split but Diageo has confirmed it will be taking responsibility for the Jamaican lager Red Stripe, as it owns a majority share in its owner Desnoes and Geddes.
Earlier this year Diageo boss Simon Litherland told the Morning Advertiser that the growing world beer category was an opportunity to grow Diageo's beer business in the UK and the company has since launched Namibian brand Windhoek into the market.
Well's & Youngs said it would be concentrating on its ales and other partner brands such as Kirin Ichiban, Estrella Damm and Erdinger, which would now "get even more focus," according to chairman Paul Wells.
"Both Red Stripe and Corona are in great shape and have experienced outstanding sales in the last few years, as have our ale brands" he said.
"We always knew both contracts would expire in 2011 and we have planned accordingly."