Chelsea Football Club has “apologised profusely” to Gary Johnson, who the club says “suffered unacceptably” while a youth team player in the 1970s.

The London club said it had “no desire to hide any historic abuse we uncover from view”.

Chelsea said an external review would examine whether it carried out a proper investigation when the allegations of sexual abuse first came to light, and why it did not report them to the Football Association.

“We are fully committed to ensuring the safety and well-being of all children and young people who are in our care or attending our premises,” Chelsea said in a statement. “Their welfare is of paramount importance.”

It was previously claimed that Chelsea paid off Johnson, who alleged he was abused by former employee Eddie Heath.

Johnson said he was paid £50,000 not to go public with allegations that he was sexually abused by its former chief scout. Chelsea said on Tuesday that it had appointed an external law firm to carry out a formal investigation into a former employee.

Heath, who was the club’s chief scout from 1968 to 1979, died before the allegations were made.

Chelsea said that it was unable to identify “any further individuals who may have been subject to abuse” from the “limited information the club received” when it was made aware of the sexual abuse claims in 2014.

“The decision to have a confidentiality clause in this case has been subject to significant scrutiny,” Chelsea said, adding: “In light of what we know now about the widescale abuse in football clubs in the 1970s and 1980s, [the board] now believes that the use of such a clause, while understandable, was inappropriate in this instance.”

The statement comes after former Chelsea star Alan Hudson said it was common knowledge that former coach Heath “was a danger to us youngsters”.

Hudson, a midfielder for the club between 1968 and 1974, spoke out on Facebook after it was claimed that Chelsea paid off Johnson.

It comes as reports surfaced suggesting that a former employee of Southampton FC accused of abusing young players in the 1980s was still working in the sport.

BBC Radio 4’s Today programme said it understood the former staff member left Southampton after concerns were raised regarding his behaviour towards members of the club’s youth team.

The employee’s alleged inappropriate conduct at Southampton included making the young players line up naked in a changing room for inspection, according to testimony from an unnamed former player now in his forties.

It’s believed he was the fourth former player at the club who had come forward with allegations of abuse against the same man.

The Today programme claimed the staff member went on to work for other clubs, and – despite being asked to leave one of them – was still working in the game.

Southampton has previously indicated it would work with Hampshire police after becoming the latest team to receive information in relation to alleged historical child abuse as a major investigation into the issue in youth football continues across the country. The club has been contacted for comment.

Alan Shearer, the former Southampton player and England captain, urged footballers to come forward with allegations of sexual abuse.

Shearer said he was “shocked and deeply saddened” by recent revelations and appealed for victims to contact the NSPCC’s football helpline, which has received 860 calls in a week.

The former striker, who also played for Newcastle United – another of the clubs under scrutiny, said anyone who has suffered abuse in the sport, or was still suffering, should come forward.

Current England captain Wayne Rooney has also joined figures including women’s captain Steph Houghton, in a video on “safeguarding” published for the FA and NSPCC.

In the clip, which has been published on the FA official Twitter account, Rooney urged any young girls and boys “upset, hurt or scared with the way someone behaves with you” to “let someone you trust know now”.

Find out the full details about the four steps to #safeguarding https://t.co/FBecMg5at0 pic.twitter.com/UOhzTQraSx — The FA (@FA) December 3, 2016

West Midlands police also said it was “investigating four historical allegations of child sexual abuse in football” and Kent police said it had received reports of abuse within the county’s football community.

Ten suspects have been identified as the scandal continues to winden, and Greater Manchester police said it was investigating reports from 35 people, with its inquiry growing on a “daily basis”.

The NSPCC hotline is available 24 hours a day on 0800 023 2642