Interbrew's £2.3billion takeover of Bass could signal the beginning of the end for real ale, say UK brewers.
Competition authorities are likely to force the Belgian giant to quit brewing Bass ale brands, placing a question-mark over their future. The deal also increases the dominance of huge lager brands such as Stella Artois.
A spokesman for the Independent Family Brewers of Britain said: "Within a few years it could be the exception rather than the rule to find a pub that offers traditional draught beer."
He added: "If the deal is cleared by the European Commission, the future of Bass real ale brands may well be called into question. Foreign brewers are more likely to concentrate on one or two global lager brands and cask ale may well be a casualty of their takeover."
Peter Haydon, general secretary of the Society of Independent Brewers, said:
"We are very worried by this. The big pubcos want to buy leading lager brands and are squeezing smaller ales out. This latest deal will allow the leading lager brands greater access to the market at the expense of real ales on the bar."
Interbrew is thought likely to close at least one of the nine UK breweries it now owns, following the Bass deal and the £400million takeover of Whitbread Beer Company.
UK brewers blame high UK duty rates for the exit of Bass and Whitbread. They have been competing on an uneven playing field with the likes of Interbrew for many years.
The Amalgamated Engineering and Electrical Union is demanding urgent action from the government to save 50,000 brewing jobs with an initial 2p cut in beer tax to fight bootlegging.
Rob Hayward, chief executive of the Brewers and Licensed Retailers Association, said: "We are extremely pleased. We will be contacting them to see if we can pursue this."
He hinted at the possibility of a new joint campaign on duty.
In a trading statement last week Whitbread chairman Sir Michael Angus warned that the disposal of its beer company to Interbrew would hit the group's profits for the year. The company is thought likely to sell off its remaining drinks interests, which include a stake in Britvic, and its off licences.