This results in half of all eligible lesbian and bisexual women never having had a smear test, they said.
The human papilloma virus (HPV), which causes most cervical cancers, can be transmitted through lesbian sex.
Cervical cancer charities say all women, no matter their orientation, should have regular cervical screening.
Lesbian, gay, bisexual and transgender (LGBT) groups say women regularly face barriers to accessing healthcare and can have poor experiences when they do.