CAMRA say they will ask 65,000 festival-goers to write to their MPs
Thousands of pubs around Britain face being put out of business by high beer taxes, campaigners complain.
The Campaign for Real Ale (CAMRA) is taking its protest about price increases to the opening of the Great British Beer Festival in London.
It said protesters at Earls Court would wear "fair deal on beer tax" T-shirts and masks of Alistair Darling.
Visitors to the London venue will be urged to ask their MP to lobby the chancellor for a beer tax rethink.
In March alcohol tax rose 6% over inflation and is due to do so again by 2% for each of the next four years.
CAMRA chief executive Mike Benner said: "High beer taxes threaten to prevent many low and moderate earners enjoying a regular pint at their local pub.
"We desperately urge the chancellor to think again before he goes down in history as the chancellor who closed thousands of community pubs, damaged community life and prevented many millions of pub-goers from enjoying a regular trip to the pub."
CAMRA said in the run-up to the festival more than 1,700 people had joined a Facebook group - "Fair Deal on Beer Tax" - to call for lower excise duty on beer.
In March drinks industry representatives warned the tax changes would add up to 4p to the price of a pint, leading to more pub closures as drinkers went elsewhere for alcohol.
They also said it would do little to curb binge drinking because drinkers would switch from pubs to cheap shop-bought alcohol.