A former chief of staff to the U.K.'s Brexit minister says he will launch a new political party next month with the goal of keeping Britain in the European Union.

James Chapman says he will officially kick off the centrist party, called the Democrats, at the People's March for Europe rally in London on Sept. 9.

Chapman worked for Brexit Secretary David Davis until June, and has since become a vociferous critic of Britain's decision to leave the 28-nation bloc.

In a statement released Tuesday by People's March for Europe organizers, Chapman said the party's goal would be "to reverse Brexit with no second referendum."

Chapman has called for pro-EU members from both government and opposition parties to join him. So far, no lawmakers have publicly heeded his call.