Referee Mark Halsey has received abuse on Twitter after sending off Jonjo Shelvey and giving Manchester United a controversial penalty in their victory over Liverpool at Anfield on Sunday.
The abuse has been condemned as "beneath contempt" by the referees' union, Prospect, which said it would provide any assistance he required.
Halsey, who was diagnosed with throat cancer in 2009 but returned to refereeing in March 2010 after successful treatment, showed Shelvey a red card for a challenge on Jonny Evans and awarded the late spot-kick from which Robin van Persie secured a 2-1 win.
A tweet posted from an account named @johnwareing1 read: "I hope Mark Halsey gets cancer again and dies", while another from @lfcjohn259 read: "Mark Halsey should've died of cancer."
Both tweets generated a furious response on the social media site. That from @lfcjohn259 was deleted, while the @johnwareing1 account was removed completely.
Halsey's wife, Michelle, was also sent abusive messages. Reports suggest that the referees' governing body, Professional Game Match Officials Ltd (PGMOL), will offer Halsey the opportunity to consult a psychologist should he wish to, but he is set to referee the Capital One Cup game between Southampton and Sheffield Wednesday on Tuesday as scheduled.
In a statement, the Prospect national secretary, Alan Leighton, said: "Prospect wholeheartedly condemns the unacceptable abuse aimed at Mark Halsey on Twitter. The comments, made by a very small minority, will be seen as beneath contempt by all decent people.
"The main concern now is for Mark and his family, who are receiving the support of his employer, PGMOL. Prospect will also provide any assistance as required.''
PGMOL said it abhorred "any abuse of match officials, whether that is in stadia or outside them" and added: "Our main concern is towards Mark and his family and, as with all match officials, there is a backroom team who are there for them."