The British Transport Police faced fury on social media after sharing a picture of their officers grilling a passenger during a spot-check before quickly deleting it.
The Welsh force were called "shameful" for uploading the image during the 17-day firebreak lockdown in Wales.
The country is currently in the middle of a national shutdown to try and control the spread of coronavirus.
British Transport Police didn't judge the mood well when they tweeted a snap of their officers in action as they crowded around a seat on a train service on Saturday.
They captioned the picture: "We are checking if your journey is essential! Please stay at home!"
But they soon back-tracked and were forced into an embarrassing climbdown.
After an angry response, officials deleted the post altogether and offered a string of clarifications.
They account said: "Right folks - the last tweet generated a fair amount of comment so let's put a few things straight.
"Wales is on lockdown. You should not be out without a reasonable excuse.
"It is our job to enforce the current regulations. We did this throughout the previous lockdown too.
"This means asking why people are travelling.
"Tonight, everyone we have spoken to has been travelling legitimately.
"The lockdown is there to stop the spread of this virus. We all need to do our bit.
"Only those who think the rules don't apply to them and selfishly break them, need to be worried about being spoken to by us.
"We want this virus to go away as much as everyone else. We all need to do our bit to achieve that."
One user responded: "No sane person wants to be treated like this. The way the police are behaving is a disgrace."
Another said: "Your manner in these tweets is very confrontational. You will lose the public on this."
A third posted: "Listen to yourselves. You have lost the trust of the people you are supposed to be serving."
It comes as a Welsh Government minister warned a second fire-break lockdown is 'likely' in Wales in early January or February.
The country is currently in the middle of a two-week national lockdown and it will not be the last such measure, according to deputy minister for economy and transport Lee Waters.
Speaking on BBC Radio Wales Sunday Supplement programme, he said: “This is not the last lockdown we are going to see."
“The projections and papers we published on our worse-case scenario projections show it is likely we are going to need another firebreak in January or February.”
