Sex robots have the potential to provide a valuable service for people who are elderly, disabled or who find intercourse traumatic, but they also carry ethical risks, experts say.

Sex robots that look like humans can already be bought or leased for parties in the US, and plans for a cafe staffed by "erotic cyborgs" in Paddington, London, have been mooted.

The authors behind the Foundation for Responsible Robotics' (FRR) report, published on Wednesday, believe they could herald a "revolution" in sex, helping people who would otherwise find it hard to have intimate relationships.

But they also raise concerns that sex robots could increase the objectification of women, alter perceptions of consent and be used to satisfy desires that would otherwise be illegal.