In a last-minute plea to MPs, Simmonds said the amendment would be “hugely damaging” for the trade and result in 1,400 more pubs closing and 7,000 job losses.
MPs are set to vote on the clause tomorrow at the Report Stage for the Small Business, Enterprise and Employment Bill in the House of Commons.
Simmonds said: “This amendment would effectively break the ‘beer tie’, ending a business model that has wide cross-party support, and has served Britain’s unique pub industry well for nearly 400 years.
“It would hugely damage investment, jobs, and results in 1,400 more pubs closing, with 7,000 job losses - as the Government’s own research shows.
“Without ‘the tie’, many much-loved British breweries, robbed of their existing market through their own pubs, would also have to close.
“Given this would reduce beer choice for lovers of real ale, it is extremely baffling that CAMRA could even begin to consider supporting such a move.”
Earnings
She added that BBPA analysis of over 2,000 signed agreements with pub companies show projected earnings for publicans of around £32,000.
“Pubs have faced very difficult trading conditions in recent years, as have all businesses in the high street. But the sector is starting to turn the corner and damaging changes by Parliament will not help.
“I hope MPs see sense, and reject these hugely damaging proposals,” she said.
However, coalition campaign Fair Deal for Your Local has produced an “MRO Top Trumps” infographic, using October 2013 data from the Federation of Small Businesses, claiming that the clause would boost employment and the UK economy.
Tom Stainer, head of communications at Campaign for Real Ale, said: "The proposed Market Rent Only option would only apply to companies who own more than 500 pubs, meaning none of the family brewers would be affected. Furthermore, a publican with a Market Rent Only option would be free to buy beer from whichever brewery they like, including micros and smaller local producers, so there is no doubt that passing this amendment would be good for real ale breweries in Britain.
"Independent research shows that 57% of licensees tied to the large pub companies report earning less than £10,000 a year - a figure that CAMRA believes is far more reliable than pub company estimates."
The MRO clause was tabled earlier this month by Parliamentary Save the Pub Group chair Greg Mulholland, BIS Select Committee chair Adrian Bailey and Select Committee member and Save the Pub Group president Brian Binley.
Further amendments to the Bill can be made at the Report Stage in the House of Commons, which finishes on Wednesday (19 November) and is followed by the Third Reading. It then moves to the House of Lords for consideration.