The nationwide pub group has reduced the price of a pint of real ale by an average of 20p, meaning more than 600 sites are now serving Greene King-brewed Ruddles for £1.69.
A further 160 pubs will be offering a pint for £1.59 or less, including 36 pubs serving them for £1.39.
The remaining pubs will sell a pint of ale for between £1.99 and £2.89, depending on each site’s location and this includes pubs in central London.
JDW chairman Tim Martin said: “At the current time, customers and businesses pay tariffs on thousands of products, which are imported from outside the EU.
“These tariffs are collected by the UK Government and sent to Brussels. Provided we can leave the customs union on 31 October, the Government can end these protectionist tariffs, which will reduce prices in supermarkets and pubs.
“In order to illustrate this point, JDW has decided to reduce the price of Ruddles bitter, brewed by Greene King.
“A lot of politicians have misled the public by suggesting leaving the customs union could be a ‘cliff edge’ or ‘disaster’. This is the reverse of the truth. Ending tariffs will reduce prices.”
He said if the deadline was met, beer prices across the JDW estate would be brought down to an “unbelievable low”.
Martin also said as long as the UK leaves the EU “properly”, with “no messing around with the customs union or any of that funny stuff”, beer in his sites would be sold at rock bottom prices.