Two football teams who played the weekend after the Queen died are being investigated and will be "dealt with in the strongest possible terms".
The rebuke at the "despicable" behaviour came from a local league in Sheffield that had ordered all matches be cancelled as a mark of respect.
Sheffield International FC tweeted on Friday that its match would be played as a friendly instead, but later said someone had "snitched on us so now even the friendly is off".
It switched to a training session, adding: "If that gets cancelled we'll have a game of rugby seeing as that's deemed respectful enough."
The team seemed to be referencing the fact that sports such as cricket and rugby went ahead after the Queen's death while nearly all football matches were postponed.
However, on Saturday morning, Sheffield International FC tweeted a picture with the caption: "Silly billies. Everyone's turned up in their match kit".
A few minutes later, another image showed them shaking hands with their opponents: "Oh wow! Byron House have arrived! Fancy seeing them here!" the club tweeted.
The Sheffield and District Fair Play League condemned the "disrespectful and despicable behaviour".
"There will be an investigation into this matter, in conjunction with the Sheffield & Hallamshire County FA, and these two teams will be dealt with in the strongest possible terms," it said in a statement.
League chairman Danny Taylor said: "Queen Elizabeth II ruled, served and led with integrity and humility for more than seven decades.
"It is a terrible shame that these two teams could not emulate this even for a single Saturday, despite our clear instructions.
"We may or may not agree with the mass cancellation of football, but this was decided as a mark of respect and should therefore have been adhered to."
The FA's decision to postpone matches - even in grassroots leagues - was criticised by some, who said they should have gone ahead to allow fans to pay respects in the immediate aftermath of the Queen's death.
Former England player Peter Crouch's tweet suggesting games should have gone ahead got 212,000 likes.
"I know it's only a game and some things are much bigger but imagine all our games went ahead this weekend," he posted.
"Black armbands, silences observed, national anthem, royal band playing etc to the millions around the world watching?
"Isn't that a better send off?"
Football matches in England resumed as planned from 12 September, but won't take place on the day of the Queen's funeral.
All Premier League matches between Friday and Sunday will ask fans to join a minute's silence, followed by the national anthem.
When the clock reaches 70 minutes, those attending will also be invited to applaud the Queen's 70-year reign.
Images of the Queen will be displayed on big screens and flags at grounds will be flying at half-mast.