The annual list showcases the UK’s best 100 public and private sector employers for lesbian, gay and bisexual staff.
Ernst & Young took the third spot last year but have moved up to first place due to a series of initiatives aiming at creating an inclusive workplace.
The organisation currently runs a network for lesbian, gay, bisexual and transgender staff as well as providing sponsorship for Student Pride and actively working to raise workplace inclusion as an issue with clients.
Liz Bingham, managing partner for people at Ernst & Young, said: “A strong commitment to diversity and inclusiveness is not only important for our people, but is also a business imperative in what is an increasingly competitive and interconnected world.”
Second place in the index was taken by last year’s winners, Home Office, while Barclays came in third.
Stonewall estimates that there are currently 1.7 million lesbian, gay and bisexual people currently in employment in the UK.
According to the gay rights charity there are a further 150,000 gay students currently at UK universities, many of whom will use the index as a tool to gauge where best to take their talents.
“Competition for a place in the Top 100 was fiercer than ever this year,” says Ben Summerskill, chief executive at Stonewall. “With new, more demanding criteria, every employer securing a position in the Top 100 has performed impressively – and the participating employers collectively employ over 1.9 million people.”
This year’s list featured 25 new entries including MI5 which reiterated its commitment to equality and diversity in the workplace.
“The Security Service has worked hard in recent years to promote equality and diversity across all areas of its work,” said Jonathan Evans, director general of MI5.
“We are pleased to be recognised by Stonewall, but there is still more we can do. We will continue to support lesbian, gay and bisexual staff to make MI5 a truly inclusive place to work.”