The beer tie forces landlords to buy their beer directly from the pub's owner and affects the amount of rent they pay.
In a research note, Jamie Rollo, a Morgan Stanley analyst, said this model "looks increasingly archaic", as it is "exacerbating the volume declines in tied pubs, which are unable to reduce price without taking a significant hit to their cash margins".
"We estimate licensee profits were under £20,000 in 17% of Enterprise's pubs and 28% of Punch's - £20,000 generally being the minimum level to make it worth running a pub," the research note said.
Rollo said this equates to £3.30 an hour each for a couple, excluding benefits of accommodation above the pub.
The Fair Pint group, which has been campaigning to abolish the beer tie, seized on the report to once again demand a reduction in rent for tenants.
David Morgan, a chartered surveyor and member of the steering group of the Fair Pint campaign, said: "This research highlights the practices that pubcos, as property companies, are increasingly employing in order to prop up their ‘archaic' business model.
"Almost every pubco rent review that I get involved with should see the rent decreased, given the current climate, but the pubcos are still demanding rent increases."
In a statement, Punch said: "We always been transparent about our rent review process which is clearly outlined in our BII accredited customer charter.
"We have always said that we will not conduct a dialogue with Fair Pint through the trade press and would urge any of our licensees, who have concerns about the rent review process, to discuss this with us directly."
By Daniel Thomas
E-mail your comments to Daniel Thomas here.