A former London NHS trust executive has said "institutional racism" is an issue within the health service, with very few senior figures from ethnic minorities in the organisation.
Around 1% of NHS chief executives are of black and minority ethnic (BME) origin, health service figures show.
Hari Sewell, ex-executive director of Camden and Islington NHS Trust, said: "The statistics speak for themselves."
The Department of Health (DoH) said the NHS was not institutionally racist.
Of the 1.4 million people the NHS employs, around 18% are from BME backgrounds, according to the NHS Leadership Academy, which promotes "best practice" for leadership within the NHS.
Mr Sewell, who has worked for the NHS across London as an implementation manager for mental health services, said: "You could say that services are institutionally racist. Institutional racism is an issue.
"The statistics speak for themselves. In other aspects of public life you get better representation."
A Department of Health spokeswoman said: "The picture of an institutionally racist NHS is not one that we recognise.
"Any form of bullying and harassment is unacceptable in any workplace - including racism - and the NHS has strong mechanisms in place to address these."
Mr Sewell said "It's a bigger issue in London."
In the capital, more than 44% of staff are from BME backgrounds, but of the 31 primary care trusts, only one has a chief executive who is from a BME group, the Leadership Academy said.
"Where you have an environment that indicates you should have a higher proportion of BME staff at senior levels, when you don't, it feels more toxic," said Mr Sewell.
Mr Sewell said he had experienced institutional racism, not at Camden and Islington NHS Foundation Trust, in north London, where he was an executive director between 2002 and 2009, but when he was working more widely across the NHS in London.
He said: "I went to deliver an event in a rural community hall. When I arrived in my suit with my brief case, I went to the office, I knocked on the door to say 'I'm Hari', and this woman turned around and said 'don't come and beat me up'.
"When I went back to my office and I said to my colleagues 'you won't believe what happened. I outlined my account and one of my colleagues said 'maybe she was trying to crack a joke and be funny.' I was taken aback.
"I thought, 'so I am on my own with this stuff?'. For me that was a sign of something that was institutional. There was a gap in their ability to recognise what it's like to be an isolated soul."
NHS London said it was "committed to equality and diversity".
Yvonne Coghill, national programme leader for equality in the health service, said racial inequality was an issue in the NHS.
"I believe it is an issue that there are not enough BME executives," she said.
"If you are working at that level and aspiring to be a senior leader and you look up and you don't see anybody like yourself up there, it's automatically going to demotivate you."
Ms Coghill said there was a "lack of understanding" as "senior leaders are not used to having people of colour mixing with them at that level".
"There's a fear in the system and it works both ways," she said.
"In the NHS, in midwifery and nursing, BME staff are more likely to be disciplined, given the sack, and take organisations to employment tribunals than white staff," she said.
A Bradford University study, which surveyed 80 NHS Trusts between June 2008 and November 2009, found BME staff were nearly twice as likely to face disciplinary procedures than their white counterparts.
The survey "found inconsistent management practices in relation to disciplinaries" which reflected "a lack of confidence amongst managers in dealing with issues relating to staff from different ethnic backgrounds".
Johns & Saggar solicitors' chairman Khalid Sofi said he had represented a number of cases where ex-employees and employees from BME backgrounds had filed discrimination claims on the basis of race or religion against various NHS trusts in London.
But he said his clients were "not prepared to discuss their cases publicly" because they "generally still work within the NHS".
One way of tackling the issues raised would be to introduce "training programmes targeted at black and minority ethnic groups and others targeted at non-BME staff", Ms Coghill suggested.
"BME people need to be able to talk about the issues they face which are very different from the issues that the majority population face," she explained.
"You also need separate training and development programmes for non-BME people."
Mr Sewell, who now works as a management consultant, suggested society needed to look at the "broader social circumstances".
"We need to think about how we enable people to overcome some of the disadvantages that might have developed in their lives," he said.
"Education, care responsibilities, housing and lower access to revenue and capital wealth, might serve as obstacles to progression."
Meanwhile, an alternative approach is being taken by a clinical community network, which is being launched in the Houses of Parliament next Monday.
African Health Policy Network (AHPN) chief Francis Kaikumba said: "To really make it in the NHS relies upon networking.
"That's how senior management decisions are made a lot of the time and BME staff tend to be not within those networks."
"We are trying to create a networking culture for BME clinicians, so they can regularly meet, share ideas and support each other - give that practical support that really helps improve their opportunities within the NHS."