Protesters from the Lesbian Avengers group scattered hundreds of leaflets inside the Barbican Hall and accused charity officials of being 'homophobic bigots'.
They slipped into the hall before the Princess arrived for the annual meeting of Save The Children, of which she is president.
During a film celebrating the charity's work, two women, both wearing black T-shirts proclaiming them as lesbians, shouted out and threw leaflets among the audience.
The Princess was attending the day-long meeting, but it was not immediately clear if she was in the hall at the time of the protest.
After being ejected by stewards, Kirsti Reeve and Donna Clark said they were kicked and punched as they tried to leave the building.
Miss Reeve said: 'Sandi was perfectly acceptable when they thought she was straight. As soon as it became clear that she was a lesbian mother they dropped her.'
Miss Toksvig, star of Channel 4's Whose Line Is It Anyway?, was at the centre of controversy last month when it emerged that she and her partner Petaline Stewart were acting as parents to three children.
Miss Stewart gave birth to the two girls and a boy after artificial insemination using sperm from a male friend.
Save The Children said its 17-strong council had decided to withdraw the invitation to the 36-year-old Danish-born comedienne because her appearance might distract from the events of the day.
Miss Clark said: 'Why can she not support saving children? Lesbians were children too.'