The GMB union is planning a demonstration outside a South London pub this morning to highlight its claim that pubcos are "overcharging" tenants for beer.
Admiral Taverns' licensee Bill Synan is expected to be evicted from his pub, the Nags Head, in Camberwell, South London, at 9.30.
The pubco says Synan is being evicted for having "continually breached the terms of his contract".
But GMB claims that under the terms of his tie, Synan, who has been at the pub for 17 years, was unable to "make ends meet" and is being evicted for paying "wholesale prices he can afford".
Paul Maloney, GMB national officer said: "While there are always many aspects in any dispute what is at the core here is overcharging.
"This is not right or fair and it is why we will be there to protest when the bailiffs come to kick Bill out of his job and his home."
However a spokesman for Admiral Taverns said its action was "very much a last resort" and "comes after numerous attempts on our part to reach an agreement with him".
"However, he has continually breached the terms of his contract," he added.
"We offer our landlords a large selection of leading drinks brands at competitive prices and all pricing agreements are negotiated with licensees on an individual basis.
"All licensees who sign up to a tenancy or lease agreement with us are fully aware of these prices when they sign up to run our pubs."