The British Beer & Pub Association (BBPA) has threatened the GMB with legal action if it does not abandon the allegedly "misleading" advice it is giving to tied licensees.
In a bold move, BBPA chief executive Brigid Simmonds has written to GMB general secretary Paul Kenny urging his union to publicly retract its assurance tenants would be immune from legal action, even if they break their contract.
If the union doesn't comply, the BBPA says it will seek an injunction to "restrain" the GMB from "inducing" breaches of contract.
Simmonds writes: "It has come to our attention… that you have asserted that Parliament has granted immunity to tied tenants in relation to trade disputes with their landlord.
"That is quite simply misleading and wrong."
In the letter she calls on the GMB to make it clear publicly there is an "absence of immunity" and urged the union to "not take any steps, whether by ballot or otherwise, likely to have an effect of inducing any tenants" to breach their agreement.
Simmonds adds: "In the event that you do not we reserve our position and without further notice may instruct our solicitors to seek an injunction to restrain you from inducing breaches of contract and seek damages and the costs incurred in such an application."
The letter dated yesterday (March 15) comes on the day the GMB is due to meet with pubs minister John Healey and hold a lobby day in Parliament.
But it appears BBPA members have run out of patience with the trade union and called on Simmonds to take action.
The letter argues the relationship between pub tenants and landlords is not of "worker" and "employer", so any dispute does not come under the Labour Relations (Consolidation) Act 1992.
Simmonds also suggest any efforts by the GMB to "induce" tenants to break their contract could leave the union open to an "unlimited" damages claim from pubcos.
"Ultimately tied tenants do risk losing their business and their homes and could face insolvency when potentially disproportionate legal costs would be sought from them," the letter adds.
The letter has been endorsed all the BBPA's main pubco members - including Enterprise Inns, Punch Taverns and Admiral Taverns.