The Leicester City forward Jamie Vardy has apologised for a “regrettable error in judgment” and will be investigated by the club over a video showing him allegedly using racist language.

The Sun on Sunday published footage, reportedly taken in the early hours of 26 July, that appears to show the England international abusing a fellow gambler in a casino and calling him “Jap” on three occasions.

In a statement released by Leicester to the Press Association, the 28-year-old said: “I wholeheartedly apologise for any offence I’ve caused. “It was a regrettable error in judgment I take full responsibility for and I accept my behaviour was not up to what’s expected of me.”

Leicester issued their own response, promising to look into the incident. “We expect the highest standards from our players on and off the pitch and for them to set an example as role models in our community,” read a statement. “We have noted Jamie’s apology and will begin a process of investigation into the incident imminently. There will be no further comment until this process has concluded.”

Leicester are owned by the Srivaddhanaprabha family from Thailand and it is only a matter of weeks since they terminated the contracts of Tom Hopper, Adam Smith and James Pearson, son of the former manager Nigel, for their conduct on a close-season tour of the country.

The trio had featured in a sexually-explicit video during which racist language was used and were sacked following an internal investigation.

At the time they noted that: “[The club] is committed to promoting a positive message of community and family values and equality, and to upholding the standards expected of a club with its history, tradition and aspirations.”

The anti-racism organisation Kick It Out had earlier called on Leicester to act; its director Roisin Wood told the Sun on Sunday: “It is disappointing that the opening weekend of the season, which should be a time of celebration, has been overshadowed by these allegations.

“Footballers, no matter the level they play at, are role models on and off the field and their behaviour can impact millions of fans across the country.

“If these allegations are proven, we would consider it to be a serious matter and would expect the club to conduct a swift and thorough investigation. We have contacted the club and await their response.”

Vardy, who opened the scoring for Leicester in their 4-2 opening day victory over Sunderland, was a late bloomer at the highest level. He was still playing non-league football with Fleetwood as recently as 2012, but made his name following a £1m move to Leicester.

He scored 16 times as the Foxes won promotion to the Premier League, then scored five times last year as the team fashioned an unlikely escape.

Vardy was rewarded with a maiden England call-up by Roy Hodgson, making his debut as a second-half substitute in the 0-0 friendly draw against the Republic of Ireland.