A campaign to end the beer tie will officially be launched at the Houses of Parliament next week.
Fair Paint is calling for action to help UK landlords and consumers who suffer as a result of tied lease agreements.
It will be launched on Tuesday by MP Tim Farron who has previously posted an early day motion calling for an end to pubco power.
A Fair Pint spokesman said: "The campaign is calling for fairness for UK landlords and consumers who suffer as a result of 'tied lease agreements'. Approximately, 24,000 British pubs (37 per cent) are owned by pubcos.
"These "tied" landlords have no choice but to buy their beer from the pubco even though they can buy the same beer cheaper elsewhere.
"Tied pub landlords also have to rent their pub and home from their pubco with rents which are profit related. Unfortunately, upward-only rent reviews and beer that has to be bought at inflated prices from the pubco places enormous pressure on many tied landlords who struggle to make a living.
"Huge numbers of landlords are simply being forced out of the market and few consumers understand why they are paying more for their pint."
The campaign is calling for the tie to be removed from all pubs -except those owned by brewers with 500 pubs or less.