The story that shocked her most, Esther Wilson says, was the mother who bought a pair of boots for her boy serving in Iraq. The ones he had been given were useless, the woman said; they were melting in the heat, her son was getting foot rot. So she bought him a new pair. Only she couldn't afford to post the two together. She had to send one, then wait till the next benefit payment had come through to send the other. "I just thought, this is amazing," Wilson says. "Those young men are out there, being brutalised, fighting, their lives in danger, getting shafted every which way - and we're not even giving them decent boots? How come we've none of us heard about this? How come no one gets to know?"

Thanks to Wilson's new play, Ten Tiny Toes, a few more people will now get to know. Not just about the boots that desperate mothers are sending to their sons - British troops serving in Iraq and Afghanistan - but also the T-shirts, the foot cream, the plasters, the soap, the bottled water, the teabags. The kind of things you could be forgiven for thinking a 21st-century army might be able to provide.

What Ten Tiny Toes mainly shows, though, is what happens to a very ordinary, loving northern family, when a distant war suddenly comes into their living room and, as Wilson puts it, "the cracks appear"; what becomes of a woman when the love and pride she feels for her son is matched only by her fear for his safety - and her unshakeable belief that the cause for which he is risking his life is wrong.

It is gut-wrenching stuff.

"I cried," admits Lily, who watched the play the other night with a group of fellow army mothers whose conversations with Wilson helped provide its raw material. "None of us thought the characters could have been any better if we'd been portraying them ourselves. Some things you see about the war are in your face - this one was in your heart. It's amazing seeing the precise emotions you've been feeling just up there on stage."

Lily's son, who she does not want to name for fear of upsetting him further, has done three tours of duty in Basra. Linda's has seen service in Bosnia, Iraq and Afghanistan. "I just get so angry," she says. "If Iraq was a legal war, if the troop numbers were adequate, if their equipment was up to scratch and they weren't driving around in lousy Land Rovers when everyone else has proper mine-protected armoured vehicles, maybe it would be more bearable. But it isn't. Do you know, other soldiers over there call the British troops the Borrowers? They've never got enough of anything. Not even toilet paper, sometimes. And they're risking their lives and dying."

Ten Tiny Toes was born after Wilson's previous script - she was the lead writer on Unprotected, a widely praised verbatim docu-drama based on more than 1,000 interviews with residents, politicians, police, clients and workers in the Liverpool sex industry - won the Amnesty award for Freedom of Speech at the 2006 Edinburgh Festival. Born in the north-west, Wilson, who has spent most of her life in Liverpool and has two grown-up sons, was an actor and university drama teacher before winning a BBC playwriting bursary five years ago. After Unprotected, Liverpool's Everyman theatre was interested in more of her work. "I wanted to write a play about love and I was just fascinated by these soldiers' mothers," Wilson tells me in the Everyman bar. "As a completely neurotic mother myself, I had no idea how they coped. I had heard loads of war stories, but nothing about them."

She began putting out feelers in the summer of 2006, and the response was "massive, and amazing. I had mothers telling me they were trawling army surplus websites to buy essential gear for their sons. Mothers whose boys had lost their lives were telling me that while it wouldn't make them cry any less if they knew their sons had died in a noble cause, it would at least make them feel better. It was honest, raw. Authentic."

Most of the women Wilson spoke to she met through Military Families Against the War, the organisation for relatives of servicemen killed and still serving in Iraq, which was co-founded by Rose Gentle after her son Gordon, 19, died in a roadside explosion in 2004. The group is unequivocal: it wants all British troops pulled out immediately from a war it says is "based on lies ... an unjust war for political ends". While its members have asked repeatedly to meet Tony Blair, both as prime minister and since, and Gordon Brown, neither politician has so far consented to meet with the relatives of any British soldier killed on active service.

Wilson says she worked hard not to portray just "the standard liberal view" of the war. "I tried to take a rounded view. There are lots of people who really do believe that what we're doing in Iraq is right, and that viewpoint is properly represented in the play. In the end, what I decided to do was focus on one family, and see if we can't make connections to a wider world."

The family in the play are the Liverpudlian Kents: Gill, the chirpy mum; Mike, the affectionate but recently out-of-work father; and sons Michael and Chris. Michael has already enlisted and the play begins with his joyful return from a tour of duty in Iraq. Chris, fired up by wargames and fed up with a dead-end job in a menswear shop in a country where "people just want to buy things; they don't want to make things any more", joins up in the course of the play. Ten Tiny Toes explores the reasons why such men do join up. "The army doesn't recruit well in London," Wilson says. "It does very well in depressed, working-class white communities, places where often the only real alternatives are guns, gangs, drugs."

It dwells, too, on the part modern technology plays in the way families experience the war. "The internet gets your head into that warzone," she says. "In the second world war people had to wait weeks and weeks for news, for the letter to come. Today you can watch people being beheaded if you want to, you can see soldiers being blown up. Families, especially mothers, are glued to their screens, permanently plugged in. The war is in their living room."

The inspiration for Wilson's remarkable play is a unique group of mothers "who channel all that anger, all that rage, into an unending search for truth and justice. I was humbled by meeting them. They are immensely strong women, resilient and witty and sometimes very funny. It wasn't a miserable experience at all, far from it."

For almost all the women involved in Military Families Against the War, this was a first campaigning experience. "I'd never got involved in anything like this, never protested against anything," says Lynda. "I've never been a political person. But I believe this war in Iraq is an illegal war, a war for which this country was completely unprepared and is determined to wage on the cheap, with no regard to the safety of the people fighting it. They're not looked after properly when they come out, either. And it's my son out there, putting his life on the line. Wouldn't that make you angry?"

Campaigning, says Lynda now, "helps me vent my anger. It makes me feel that I'm doing something. I still have my days, of course. I'm frightened to go home, I can't sleep, I'm afraid to answer the phone. Every time a car pulls up outside, I'll listen to hear if it's one door that slams or two. If they're coming to tell you your son has been killed, they always come in twos."

Perhaps most upsetting of all is that the mothers' vocal opposition to the war and persistent attempts to lobby ministers for better equipment and a full withdrawal often cause problems for the sons. "Often the response is: stop talking about what you know nothing about - you just don't understand, that kind of thing. Some are embarrassed, some get really angry, some actually stop talking to their mums. Some get into trouble in the barracks, or stick from their commanding officers," says Wilson. Even if mothers supported their boys going into the army, are proud of them, "Their response is: I have to do this. What else can I do? I can't sit around till he comes home in a bodybag."

And does this warm, heartfelt, at times searing work have a campaign message? Wilson is not sure. "Maybe it's just about people who love."

At bottom, perhaps, the unanswered question behind Ten Tiny Toes is whether these mothers' determination to fight, rather than surrender and move on, is the only way they can cope with such an impossible burden of fear, anger and grief. "That, nobody can tell," she says. "But maybe that's the great thing: out of this horror they may achieve something good. Through what's happened to them, they have found a real, forceful political voice."

· Ten Tiny Toes is at the Liverpool Everyman theatre until July 5.