The ethnic diversity of the heads of Britain’s largest companies is declining.

A study by Green Park into the top 10,000 executives in the FTSE 100 shows a significant decline over the past 12 months with the number of ethnic chief executives falling from 6 to 4.

In total the FTSE100 has lost the equivalent of 40 of its 480 non-white leaders, meanwhile the number of all-white boards has grown by 11% to 70.

Britain’s “widening diversity deficit” is threatening Britain’s competitiveness and putting UK companies at a disadvantage when doing business on a global scale, the study by London-based executive recruiter Green Park warns.

There are no ethnic Chinese or Asian executive directors in the FTSE 100, despite the growing importance of Asian economies as trading partners, said the report.

Sandra Kerr OBE, Race Equality Director, Business in the Community, comments that ethnicity gap in leadership has been widening for years, she said “With research from McKinsey showing that the most ethnically diverse companies outperform the least diverse by 35 per cent, it’s vital that employers address this issue to ensure their workforce is able to compete in a diverse global environment.”

“The Financial Reporting Council has clearly indicated that next year, the definition of ‘diversity’ should be expanding to include ‘and race’ in the UK Corporate Governance Code. This will have a significant impact on employers by reinforcing the importance of embracing diversity, including race, and encouraging them to ‘future-proof’ their workforce for changing demographics.

“However, when only eight BAME FTSE 100 board members have British nationality, it is clear that the talent pipeline needs tackling. Gender and Race Benchmark 2014 shows that BAME people are less likely to be identified to be rated as ‘high potential’, be ranked in the top two performance rating categories, or have leadership training made available to them. These are often the key identifiers that feed the pipeline into leadership roles. We need employers to ensure that their performance and appraisal processes are fair and transparent so that all staff have equal opportunity to progress in their careers.”

In contrast it is clear that the case for gender diversity is improving. More women now hold senior executive positions in the FTSE 100, after a high-profile campaign to narrow the gender gap. Women account for 23.5pc of leadership positions, according to the latest report from Lord Mervyn Davies, who is leading the government campaign.