Media playback is unsupported on your device Media caption Maggie Harris: "I had more kidneys than I needed, so it was time to offload one."

The number of living people giving one of their organs to a stranger almost tripled last year in the UK, according to new figures.

The Human Tissue Authority (HTA) approved 104 so-called altruistic organ donations in 2012-13 compared with 38 the previous year.

The figures include the first case of someone giving part of their liver to someone they had never met.

Altruistic donations now make up about one in 12 of all living donations.

The total number of living donations, including those to family members or friends, rose from 1,217 to 1,243 over the same time period.

Diana Warwick, chair of the HTA, said donating an organ was a remarkable thing to do.

"Giving someone an organ is a brave and amazing gift. To do it for someone whom you don't know is doubly so, and the huge increase in people willing to do so is incredible," she said.

"The HTA works on more - and more complex - living donation cases every year and we expect this to continue. We remain committed to ensuring that people can donate organs with confidence."

Jan Shorrock, 36, from Lancaster, donated a kidney to a stranger in February For me, it's the same principle as giving blood, it's just a much bigger commitment. I did a lot of research into the process - I was aware you go through very rigorous psychological and medical tests. There wasn't a moment when I felt I was doing the wrong thing. I didn't really feel any doubt at all. I think a lot of people didn't understand why - it's a very personal thing. If you're considering it - do your research - it's a major operation. It's a personal thing, it's about how you choose to live your life. For me it was something I could do for someone that could make a really significant difference to their life and to their family.

The HTA believes the number of living organ donations is rising, as public awareness spreads.

Lisa Burnapp, lead nurse for living donation at NHS Blood and Transplant, said donors were motivated by a decision to do something genuinely good for someone in need.

"The increase in non-directed altruistic living donors has exceeded all expectations and means that more patients can benefit from a successful transplant and enjoy life with their families and loved ones," she said.

"This is an incredibly important gift and we are indebted to people who choose to donate in this way."

There are currently about 10,000 people in need of a transplant in the UK, with three people a day dying due to the lack of suitable available organs, according to NHS figures.

Potential living donors undergo extensive medical and psychological screening.

This includes an independent check, which ensures that the donor understands the risks involved, is not under any pressure, and that no reward has been offered.