IT company IBM has been rated the most gay-friendly company to work for by gay rights organisation Stonewall.

The firm was rated best employer in the charity’s annual Top 100 Employers List.

It was praised for its “investment in diversity” and Stonewall cited its policy of “intensive” diversity training for line managers.

IBM also won the accolade in 2007 and is the first employer to top the list twice.

UK and Ireland chief executive officer Brendon Riley said his company was “extremely proud” to win the award.

He said: “Since last year’s award, we have done much to re-evaluate and strengthen our LGB strategy as part of our overall commitment to diversity. We’ve looked more closely at the LGB network group – its value proposition and its life-cycle – to ensure that it continues to deliver value, both to the corporation and to its members.

“At IBM, we pride ourselves on delivering a working environment which reflects equality of opportunity and experience for all. Diversity constitutes our character, our identity and ultimately our success – it is in our DNA.”

The most improved employer was Nottinghamshire Healthcare NHS Trust. It was the best-performing employer in the health sector and was praised for measures such as “theatre-based diversity training”, along with raising the rainbow flag for LGBT History Month.

Hampshire Constabulary was the public sector employer of the year for the second year running. It came second in the top 100 list behind IBM.

Brighton & Hove city council came third in the top 100 list, as it did in 2009.

Accountancy firm Ernst & Young was found to have the best LGBT employee network group, EYGLES.

Stonewall said that over 350 employers applied to be part of the index, a doubling of the numbers since it began in 2006.

The index is based on a range of key indicators including a survey of more than 7,000 gay, lesbian and bisexual employees.

Three quarters of lesbian, gay and bisexual staff agreed that the workplace culture of their organisation was inclusive of lesbian, gay and bisexual people.

Staff satisfaction was higher among staff working for the top 25 employers (75 per cent) compared to lesbian, gay and bisexual staff working for employers outside the top 100 (66 per cent).

However, the survey found that bisexual staff were more likely to be dissatisfied with their employers than lesbians and gay men. They were eight times more likely to keep their sexual orientation a secret in the workplace.

Stonewall chief executive Ben Summerskill said: “As the results of the Stonewall Top 100 Employers 2010 demonstrate, even at a time of economic turmoil the best employers are choosing to recruit and retain the very best talent regardless of their sexual orientation.

“Participating in Stonewall’s Workplace Equality Index is a tangible commitment to LGB employees, customers and service users. Stonewall is delighted to recognise the contribution that each of the organisations featured in our Top 100 Employers has made to improving Britain’s workplaces. We look forward to continuing to work with them.”