A third of top companies in the UK are being accused of withholding information from annual reports, giving an "incomplete" picture of business performance.
Many organisations are failing to include details of health and safety incidents, data breaches, skills challenges and employee turnover, it was claimed.
Three business groups urged firms to disclose the contribution of staff after finding that some were not being transparent about workplace issues in corporate reports.
The study of FTSE 100 companies was carried out by the Chartered Institute of Personnel and Development (CIPD), the Chartered Management Institute (CMI) and the Chartered Institute of Management Accountants (CIMA).
Charles Tilley, Chief Executive of CIMA said: "This report shows just how big a shift is needed. We have to recognise people as the key to creating and preserving value.
"Failing to do so opens up major risks - and means that huge opportunities will be missed - because business leaders, investors and other stakeholders won't have the data they need to make the right decisions."
Peter Cheese, Chief Executive of the CIPD, said: "With many more questions being raised about corporate cultures, diversity, engagement and wellbeing, as well as the changing nature of the workforce and how these impact productivity and risk, we need greater transparency and consistency of human capital reporting."
Ann Francke, chief executive of the CMI, added: "If managers don't have sight of good people measures, they have a huge blind spot about performance and can't make the best decisions about their business."