A couple who had the nerve to ask their friend to pay up after she house-sat for them for a month have been savaged online.

The housesitter, from the UK, took to parenting forum Mumsnet to ask whether she was being unreasonable to be upset by her so-called friends' demands, news.com.au reports.

The woman did not eat any of her friends' food or drink their wine, and kept electricity and water usage to a minimum, only watching television and using the couple's computer once.

She explained her partner stayed with her as well most nights, but that the only item that had to be replaced was a single shopping bag she had left behind on a bus by accident.

"I house-sat for some friends and they've billed me!" she wrote.

"They've been away for a month-long honeymoon and asked if I'd like to flat-sit. I jumped at the chance because it's lovely there and it's much closer to where I work.

"I didn't eat their food. I didn't drink their wine. I fired up the computer once to complete a learning module."

The woman tidied the place and even left a thank you note.

"I cleaned before I left and changed their sheets for them. I left milk and fresh bread and a note saying thanks!" she said.

"This morning I got a message to say 'thanks for looking after the place. All right if we ask for a donation to cover a few bills? £300 ($580) okay?'

"I don't think if you ask someone to house sit you get them to sub your bills. Do you?!"

The woman said her partner had "half agreed to give them a 'token' amount when he was drunk with them at a pub quiz night" but that £300 was far from a token gesture.

Unsurprisingly, the couple's request for a "donation" has been savaged online.

One commenter wrote, "They sound deluded!" while another branded them "cheap b******s".

One asked, "are they taking this piss...?" and another posted, "What the hell?! They want to charge you for doing them a favour?"

Another wrote: "Why are you friends with such vulgar people? This is beyond bad manners."

Several posters suggested the woman should send her friends a bill for the same amount to cover her "house-sitting services", or to laugh the request off as a late April Fool's joke.