The presenter quit This Morning - which he had hosted for more than 20 years - after admitting to an "unwise but not illegal" relationship with a younger male colleague, who also refused to participate in the review.

Schofield admitted lying about the affair and was dropped by his talent agency, YMU.

Of 48 people interviewed by Jane Mulcahy KC, who led the review, only one reported any knowledge of the affair - a former junior member of staff, the barrister said.

They did not report their knowledge at the time, Ms Mulcahy added, and "nor did others report suspicions from much earlier in 2017".

Many junior employees "remain convinced that to speak out will have a detrimental impact on their careers", Ms Mulcahy said.

That is despite her having "no doubt" that senior ITV management are "absolutely wedded to the importance of an open culture".

However, that culture is "not filtering down to junior employees", Ms Mulcahy said.

In future, she is recommending that ITV set out clear guidelines to ensure good behaviour "even by those who are household names".

ITV's management "made considerable efforts to determine the truth" about the affair, the review found.

But in the "face of the denials of the individuals involved, ITV was unable to uncover the relevant evidence", it added.

Ms Mulcahy said it was "clear" that Phillip Schofield's "patronage" assisted his younger colleague in the "early days of his time at ITV".

Beyond that, however, he appeared to have "made his way on his own".

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In a letter in August, Schofield's lawyer said the presenter "reluctantly declined" to participate in the review because of the "risk to his health", adding that his "mental health has since deteriorated".

Regarding the young man with whom Schofield had an affair, a letter from his lawyers said he "wanted to move on with his life and was not prepared to assist with this review", Ms Mulcahy said.

Because it was not a statutory inquiry, the KC had "no power to compel people to cooperate" and all who did so spoke on a voluntarily basis.

A number of them had questions or concerns about confidentiality, she added.

Those spoken to included people in senior and junior positions, current and former staff, people on air and those managing "on-screen talent".

Ms Mulcahy is now emphasising the "importance of junior employees at ITV having the confidence to raise concerns to management in line with ITV's 'Speaking Up' policy".

She added: "I have no doubt that senior management are absolutely wedded to the importance of an open culture.

"But this culture is still not filtering down to junior employees, many of whom remain convinced that to speak out will have a detrimental impact on their careers."

Her report recommends increasing efforts to ensure staff can raise concerns. It also recommends publishing a talent "charter", setting out key standards to be upheld.

Andy Cosslett, ITV chairman, said: "We are completely committed to creating an environment where everyone is treated with respect and feels able to give of their best.

"Our promise to those we work with is that where a complaint is made, or serious concerns raised, we will always investigate and if we find that something inappropriate has happened, we will take action.

"We will continue to develop our efforts to give junior colleagues the confidence to speak up if they have something to raise."

The external review was announced by ITV chief executive Dame Carolyn McCall in May.

Its remit was to carry out an external review of the facts following Schofield's departure from the broadcaster.

ITV said it had investigated "rumours of a relationship" between Schofield and a younger employee - but the pair "repeatedly denied" the affair.

Schofield had originally said he was leaving This Morning because he had "become the story" following rumours of a rift between him and co-presenter Holly Willoughby - who quit the show herself in October.

He joined the show as a presenter in 2002 and first hosted it with Willoughby in 2009.