ONLY a few years ago, Jack Monroe had a budget of just £10 a week to feed herself and her baby son.

But when her blog, A Girl Called Jack, which detailed the thrifty meals she cooked, gained in popularity, Monroe went from being a skint single-parent to being dubbed the 'poster girl for austerity' by newspapers across the world.

Such is the success of her writing that the blog - which she started as a response to a local politician's spiteful comment about single parents - has now been turned into a cook book, also called A Girl Called Jack, and Monroe's fronting a new Sainsbury's advertising campaign. Clearly, it's all quite a lot for the 26-year-old from Southend-On-Sea to take in.

"I get a lot of messages from people saying that the blog is really inspirational and has changed the way they shop and think about food, or they're cooking different things for the family or learning to cook," explains the mother-of-one, who often bakes with her three-year-old son and her partner's three-year-old daughter.

"[The blog] reaches out to people on so many different levels, it's amazing really. I didn't set out to do any of this, I was just doing what I did and I'm constantly humbled and overwhelmed by how much people have seemed to have taken to it."

While life is looking rosier for Monroe, who is an active campaigner for Oxfam and Child Poverty Action Group, at her lowest point she "deliberately isolated" herself, because "I didn't want to admit to people how bad things were". If her success has proved anything, she says, it's that people are naturally supportive and kind.

"I haven't done this all by myself," she says. "I've done this with a lot of help, love and support along the way, and one of the things that has really hit home in the last year is that people are inherently kind and good, and I think I've seen the very best side of human nature."

Now in a better position, with her first book well received, it would be easy, you'd think, for Monroe to splash out on her weekly shops. But she's eager to maintain her thrifty habits, and confidently rattles off the prices of store cupboard essentials, quickly pointing out a price increase for tinned tomatoes.

"My cooking hasn't changed," she says. "I still cook and eat the same way I did but there's less anxiety around it now. I know I'll open the fridge and there's food in there. I've not abandoned my principles; I still cook using basic food, I use leftovers and I cook seasonally.

"The only thing that has really changed is that I've started to think about ethical eating. I'm very lucky that the tea, chocolate, sugar and bananas at the supermarket I shop at are all Fairtrade and that's right down to the basic range."

But she's acutely aware of the pressures people living on the breadline are under.

"I now buy free range eggs and meat, but when I was living on £10 a week I knew it was not possible and that's fine," she explains. "I'd never dream of telling people what to do; I just make the suggestions and say this is what I do."

A Girl Called Jack by Jack Monroe is published by Michael Joseph, priced £12.99.