La Poste has told The Local that it has taken steps to remind staff at branches around the country that the special envelopes used to carry postal votes for the crucial EU referendum are valid and don't need stamps.
The move came after numerous expat voters reported issues on a local level with staff at La Poste apparently telling them the envelopes must have French stamps on them for them to be accepted.
That's despite the envelope clearly saying in both English and French "No stamp required" (Ne Pas Affranchir).
"I can confirm that the reply envelopes used by British citizens for the referendum have been taken into account and are properly integrated into our mail circuit for the UK," La Poste spokeswoman, Perrine Landry told The Local.
"If there is a fault with this at a post office, we are making sure to fix it as soon as possible.
"Furthermore, we are reminding post offices and the mail platforms the management of these envelopes," she said.
In recent days online expat threads have featured cries of complaints from people whose prepaid envelopes for their referendum postal votes have not been recognized by postal workers in France.
"I have tried to explain to (the Electoral Commission) that the problem is France-wide not just our département in 53," wrote Lizzie Hale, who was told that a stamp was "definitely needed".
"Why should we effectively lose our vote for following the voting instructions to the letter?" she added, apparently worried that those who didn't add a stamp would see their votes disappear.
Patrick Bell added: "A friend tried to post her vote but the post office insisted it needed a stamp. She had heard that votes arriving with stamps were disallowed."
Others have reported concern that their vote won't be counted because they simply put the letter in a mailbox without checking with a postal worker first.
Some, such as Carryn Hayward, advised other expats to buy a "poste priorité" stamp for one euro.
She said that she was advised that the envelopes without stamps "will be ignored by La Poste as they will not be paid for them".
"Why take the chance" of not adding a stamp, she asked other expats.
"I have been here 18 years, three of them as a civil servant and know only too well that public servants at local level make their own decisions. And I have seen them park in 'pending' anything they have not seen before to be dealt with at some time in the future. I can't vote but if I could and had taken the time to register I would put a stamp on the envelope to make certain my vote was counted."
The Electoral Commission in the UK said in a statement that it has "arranged for airmail postage to be paid for the return envelopes" during the referendum.
All voters need to do is drop the completed ballot into a postbox, there is no need to bring it in to the workers behind the desk.
The postal votes must be returned by June 23rd, it added.
Similar problems have been reported at local post offices in Belgium and Germany, but The Local's editions in other European countries including Spain and Sweden say that post offices there appear to be accepting the prepaid envelopes.