A petition highlighting the importance of the Post Office Card Account has attracted more than two million signatures.
The petition, organised by the National Federation of Sub Postmasters (NFSP), is expected to remain open until the end of September.
Despite the government's insistence that the card will be scrapped, campaigners remain confident the petition can help persuade ministers to find a post office-based replacement.
NFSP general secretary Colin Baker has warned of closures if this does not happen.
The next stage of its campaign will be unveiled soon.