Shadow Licensing Minister Tobias Ellwood has reportedly given his backing to a parliamentary lobby day organised by anti-pubco campaign group Fair Pint.
The group says that more than 100 MPs will be taking part in the lobby day at Westminster on May 20.
Now, top Tory Ellwood has pledged his support.
Ellwood told the Bournemouth Daily Echo that it was disappointing some pubcos buy alcohol at a discount from breweries, but then do not pass on the saving to their tenants.
"Tied pubs are having to sell alcohol at higher prices than free houses," he said.
However, he acknowledged that pubs can play a major part in helping responsible drinking.
"In 1997 the price of a pint was twice that of the supermarkets," he told the paper.
"Today it's seven times more expensive. It's easy to see why customers might be deterred from going to the pub, but in most cases that's where responsible drinking does take place."
Fair Pint welcomed Ellwood's comments. The group's Steve Corbett said: "We welcome Mr Ellwood's support. It is reassuring to see that he understands the damage being caused by the 'pubco' business model."
Annette Brooke, Liberal Democrat MP for Mid-Dorset and North Poole, is also reported to be supporting the campaign.
However, in yesterday's Sunday Times, Enterprise Inns chief Ted Tuppen claimed that a lot of what is said about the beer tie is "deliberately misleading".
"It's very easy to tell people who aren't prepared to properly understand the contracts that they pay more for their beer," he said.
"Unfortunately, the campaigners all talk about how much more they have to pay for their beer and fail to mention they are paying substantially less for their rent."
On Wednesday, a group of MPs are set to reveal the results of an investigation into the pubcos and their relationships with their licensees, including the beer tie.