The Blackpool president Valeri Belokon has suggested chairman Karl Oyston should resign after he called one of the Championship club’s supporters “a retard”.

Oyston has come under fire following revelations at the weekend that he exchanged a series of foul-mouthed text messages with Blackpool fan Stephen Smith, who Oyston referred to as “a retard” and told him to “enjoy the rest of your special needs day out”.

Oyston apologised for the incident on Monday, yet Smith rejected that and has registered a complaint with the Football Association as it came under increasing pressure to hand out a punishment.

Belokon, who has publicly feuded with Oyston recently over a perceived lack of investment in the side bottom of the second tier, has urged the chairman to walk away from Bloomfield Road.

In an interview with BBC Radio 5 live, which will air in full on Tuesday evening, Belokon revealed he would write a letter to Oyston telling him “that maybe he should go”.

He also called on the club’s fans to make their feelings known, adding: “I would like to invite Blackpool fans to write and sign an open letter for exclusion of such an attitude towards football fans.”

Belokon’s comments come after Smith, who is a spokesperson for the Tangerine Knights group which published the messages on their Facebook page, insisted Oyston’s position had become “untenable”.

The Blackpool chairman was also warned he could expect a protest against his handling of the club when the team travel to Sheffield Wednesday on Boxing Day.

Smith said: “I think it is perfectly clear the fans are going to make their opinions heard and that will be done at the next match. His apology is weak. His position as chairman is untenable. He has no choice but to resign.”

Both Smith and learning disability charity Mencap also want the FA to take action against Oyston.

Ismail Kaji, who works for Mencap, said: “I am glad Karl Oyston has apologised but using the language that he used is never justified.

“I have a learning disability and am a big football fan but I would feel ashamed to support any club that has a chairman who uses such unacceptable language to people with a disability. This language is just as bad as using racist or homophobic words and I hope the FA treats this as seriously.”

Oyston issued a statement in which he said sorry for the texts he sent and claimed the fact he received a number of abusive messages had led him to respond in such a manner.

“I would like to unreservedly apologise for any offence or distress caused by my text responses reported in the media recently,” Oyston said. “I regret stooping to the level of those threatening and abusing my family.

“My mobile number was placed on a social media website recently and it led to a barrage of abuse about my mother, father, wife, children and myself.

“In hindsight the aim of this was clear, and I foolishly opted to challenge some of the abuse, harassment and threats. Given my position, I should have acted with more responsibility and reported the abusive text messages, phone calls and answer-phone messages to the police, rather than get embroiled in such an exchange.”

Belokon and Oyston engaged in a public spat over the summer when then-manager José Riga was left with a threadbare squad because of a lack of recruitment.

Latvian Belokon, who owns a 20% stake in Blackpool, wrote an open letter to Oyston accusing him of putting financial gain over the club’s on-field interests.

Oyston hit back with an open letter of his own which insisted it was Belokon who was demanding £24m for his stake in the club.