According to Stonewall's report, The Double-Glazed Ceiling, sponsored by Lloyds TSB, many gay and bisexual women fear gender discrimination and this makes them more likely to hide their sexual orientation from colleagues.
The research pointed to a lack of openly gay women in UK workplaces when such role models are important for other lesbians.
Ruth Hunt, head of policy at Stonewall, said: "Women know in 2008 the glass ceiling is very much still in place. What this report shows is that for lesbians, that glass ceiling is double-glazed. It is no surprise Britain's two million lesbians remain almost invisible at work. Stonewall wants to see that change."
Fiona Canon, equality and diversity director at Lloyds TSB, added: "We believe employers have a vital role to play in further equality for lesbian, gay and bisexual people. Our own research shows lesbian and bisexual women face different challenges and opportunities to other staff groups and, for us, exploring this is the next step towards making Lloyds TSB a genuinely great place to work for all our lesbian gay and bisexual staff."
For lesbians the glass ceiling is 'double-glazed'
Lesbians find sexism in the workplace to be a bigger problem than homophobia, according to Stonewall.
