Facebook has removed pro-Leave and pro-Remain status update suggestions from a list given to users.
On Tuesday, Berlin-based British political blogger Jon Worth noticed that he had been given a suggested update of "in favour of leaving the EU" - but not one related to remaining.
Facebook said referendum prompts had now been removed from this list, due to the sensitivity of the vote.
The two options are shown, together, only if users search for "EU".
The British public will vote in a referendum on whether the UK should remain in or leave the European Union, on 23 June.
When Facebook users post an update to the site, it is possible to receive a recommendation for what to say regarding what they are doing or how they are feeling.
After Mr Worth looked under status update suggestions via the Facebook app on his iPhone, however, one option, "in favour of leaving the EU", appeared without another on the side of remaining in the European Union.
A Facebook spokesman denied allegations that the social network was influencing the tone of political debate on the site.
"People who search for 'EU' when they are using our status tool will see a full range of options enabling them to add if they are thinking of leaving or remaining in the EU," he said.
"People scrolling through the list of activities see options based on what their friends and other people have been using."
However, a similar issue arises in a different list when searching specifically for groups to support with a status update.
"In your list of 'supporting', you can choose Leave.EU but you cannot choose [a pro-Remain option]," Mr Worth told the BBC.
The BBC confirmed that this was still the case late on Wednesday morning.
Neither of the official campaigns - Vote Leave and Britain Stronger in Europe - are included in the list.
According to Facebook, this is because neither campaign is listed in the "non-profit organisation" category.
"I don't know how many people have actually clicked on that option in Facebook," said Mr Worth.
"Were this somehow to be replicated more widely, could it [impact the vote]?"
Last month, tech news site Gizmodo accused Facebook of intentionally suppressing stories with conservative political viewpoints in its Trending Topics section.
The company denied there was any truth to the claims.