Barnardo’s, Britain’s largest children’s charity, has been brought in by Chelsea to oversee an independent investigation into the allegations of racism that have left the club facing the possibility of widespread legal action.

Chelsea have commissioned the inquiry after receiving legal claims, initially from three former youth-team footballers from the 1990s, alleging that Gwyn Williams and Graham Rix subjected young black players to explicit racial abuse.

A fourth player, who was in their youth set-up from 1979 to 1985, has made a separate claim about the alleged culture of “continued racist bullying and abuse”, stating that it left him so traumatised he abandoned his football career, despite signing professional forms at Stamford Bridge, and struggles even to watch the current team play on television because of the flashbacks.

Three more players from the 1980s have subsequently taken on solicitors to begin their own litigation and as the Guardian revealed on Tuesday, the complainants have received public backing from two of the white players who were in the club’s youth set-up. Grant Lunn and Gary Baker decided to come forward after reading the statement Williams released to this newspaper in March to “deny all and any allegations of racial or other abuse”. Rix, who became Chelsea’s youth-team coach in the 1990s, has also repeatedly denied all the allegations.

A letter from Barnardo’s has been sent to the relevant players to inform them that an independent inquiry is under way and which supplies the contact details for the Sporting Chance clinic if they feel they need professional counselling. “Our task is to gather information about cases of non-recent racial abuse against former youth players which have been made known to the club, to look at how the club handled these matters, to compare the environment in which these alleged incidents occurred against the environment which exists at the club today, to make recommendations to the club for the future and to explore how the club may provide support to victims,” the letter states.

The investigation is being led by Julie Dugdale, the head of business at Barnardo’s Training and Consultancy, and Rod Weston-Bartholomew, the charity’s assistant director of children’s services. Dugdale has been involved in a number of safeguarding reviews and Weston-Bartholomew, who previously worked for the Children’s Workforce Development Council, is a key figure in Barnardo’s equality and diversity policy.

Chelsea said: ‘We are absolutely determined to do the right thing, to assist the authorities and any investigations they may carry out, and to fully support those affected.’ Photograph: Tony O'Brien/Action Images via Reuters

In a statement, Chelsea said: “We take allegations of this nature extremely seriously and they will be fully investigated. We are absolutely determined to do the right thing, to assist the authorities and any investigations they may carry out, and to fully support those affected, which would include counselling for any former player that may need it.”

Rix and Williams were key members of the backroom staff when Glenn Hoddle, Ruud Gullit and Gianluca Vialli were in the process of re-establishing Chelsea as one of the more glamorous clubs in the country during the 1990s. Williams, who is credited with discovering John Terry, joined as youth development officer in 1979 and was prominently involved at Stamford Bridge for 27 years.

Behind the scenes, however, one of the players to issue a legal claim has submitted evidence to the Football Association in which he describes it as a “feral environment” for some of the black players in the youth team, claiming they were treated “like a race of fucking dogs”.

According to that player’s account, in an interview with the FA’s safeguarding department, the racist abuse started after joining the club on schoolboy terms. “Even at 12, 13, the vernacular he [Williams] was using was: ‘You little black bastard, you coon, you little wog, how are you doing?’ I was a minor, I’d never heard those words being said to someone [in football]. He addressed me like that every time he saw me. He’d walk in [the dressing room] and go: ‘Hey, look at the fucking blackies here then. Fucking rubber lips. Look at their fucking big noses. You black bastard. Been fucking robbing cars, have you?’ Let me tell you something – that is the most demoralising feeling you could ever have.”

The same player also alleges Rix subjected him to physical attacks, including one incident when the former England international threw a cup of hot coffee in his face, and the latest players to come forward about the 1980s have spoken of an environment in which racism was “the norm” and Williams is said to have arranged “whites against blacks” matches in training.

Renu Daly, who represents four of the players for Hudgell Solicitors, said: “Credit to Chelsea for their stance so far in recognising the seriousness of these allegations and their commitment to ensuring these allegations are fully investigated. I am sure that has gone a long way to giving these men some confidence that they will be listened to now.”

Williams had a number of different roles during his time at Chelsea, including a spell as assistant manager to Claudio Ranieri and scouting for José Mourinho before leaving the club in 2006. Williams has been accused in the past of making homophobic comments to Graeme Le Saux, the former Chelsea defender, and was dismissed by Leeds United for gross misconduct in 2013 after emailing pornographic images of women to a number of colleagues, including a female receptionist. Williams had moved to Leeds after Ken Bates, formerly the Chelsea chairman, became the chairman there.

Rix started at Chelsea as youth-team coach but moved through the ranks to become assistant manager to Gullit and was briefly the caretaker manager after Vialli’s departure. After that he managed Portsmouth, Oxford United and Hearts, as well as coaching at the Glenn Hoddle Academy in Spain and having a brief spell as manager of a club in Trinidad. His last managerial job in England was at AFC Portchester of the Wessex League Premier Division but he left the club last August.

In March 1999 he admitted two charges of unlawful sex with a 15-year-old girl and indecent assault and was sentenced to 12 months in prison – serving six of them – as well as being put on the sex offenders’ register for 10 years. He was reinstated by Chelsea immediately after his release from Wandsworth prison and was the first-team coach when Vialli’s team won the FA Cup in 2000.