Got any spare change, Mr Gummer?

Hand outstretched, Ros Wynne-Jones went undercover with London's homeless for a week to see whether politicians' tough talk on begging is matched by their actions when no one is looking. The MPs she confronted lived up to their stereotypes

On weekdays the Environment Secretary John Gummer, the Cabinet minister responsible for the homeless, lives in a tall, semi-detached house in west London.

I'm there before the milkman, quickly chilled by the wind and rain. London is colder than you can imagine when you're sitting on concrete keeping still because there's nowhere to go.

Around 8am the minister's driver leaves Mr Gummer's house to put some bags in the boot of the ministerial Rover. He spots me sheltering by a low wall and smiles. I make a sort of grimace - my face is frozen. "Cheer up, love," he says, and gives me a wink. I can feel him watching me from inside the car as he sits there with the heaters on full blast, warming it for the minister. He waves encouragingly a couple of times.

About 15 minutes later Mr Gummer slams the garden gate, hair flying in the wind. He doesn't look at me, even though he has to step around my sleeping bag to get to the car.

"Can you spare any change?" He spins round and stares at me as if I am mad.

"Pardon?"

"Can you spare any change, please, sir?"

"No I cannot."

I feel very small. This must be what politicians mean by zero tolerance.

In the interests of political balance I'm up at dawn the next day to test the Opposition. Jack Straw, shadow Home Secretary and scourge of squeegee-merchants and aggressive beggars, lives in a suburban square on the edge of a council estate in Kennington, south London.

At about half-past nine Mr Straw appears in braces and shirtsleeves to direct his wife's car into the tight parking space outside their terraced house. I ask him if he can spare any change.

He gives me the party line: "I'm afraid I don't give money to people, I support charities instead."

"That doesn't help me much," I counter.

"Where do you live?" he asks, still not looking me in the eye.

"Nowhere, really."

"How have you got yourself in this mess?"

"My parents threw me out."

Mr Straw suddenly and inexplicably softens. He explains there is a hostel around the corner and tells me how to get there, making me repeat the directions to him. He suggests I go to the council offices and speak to the housing officer. He tells me it's all about seeing the right person in the right department. He thinks the local church should be able to help, or I could try my GP if I've got one.

Then he suddenly asks: "Are you on drugs?" I shake my head. "Good," he says. "You really should be able to get back on your feet, you know. Try the hostel."

I say I'm sorry to have bothered him and he says not at all, not to worry. He watches me disappear round the corner trailing my sleeping bag.

The following day I find myself a concrete corner out of the wind a couple of blocks from Westminster Tube station. An ideal location as businessmen, MPs' researchers and civil servants trail past in a steady stream of suits. I've been here since first light and so far I've made pounds 1.40, a cigarette and two tangerines.

In the early afternoon, Tony Banks, the Labour backbencher, hurries past with a curt shake of his head as I repeat the beggars' mantra, "Spare some change, spare some change..." Gillian Shephard, the Education Secretary, crosses the road before she gets to me, order papers clutched to her chest against the biting wind. By dusk the good people of Westminster have donated just under pounds 3.

The next day at St James's Park tube station I'm having more luck in the way of hard cash - the week's record total of pounds 4.08. At the start of the week I was concerned that my clothes weren't right, that they would look too clean or new. I needn't have worried. People don't look at you - they just register the visual shorthand of the sleeping bag and the scattered coppers and either shake out their pockets or shake their heads.

I hand the money I've made to Mary, a yellowish-haired old woman who spends most of her day asleep in shop doorways. The average life expectancy of someone sleeping rough is now 42 according to the homeless charity Crisis. In homeless person years this makes Mary about 120.

She drinks the money and you can see why - anything to numb yourself against the harsh stares and put a bit of fire in your belly. As Jenny, a homeless 19-year-old explains: "You get nothing from suits - it's the ones with the holes in their trousers who'll sort you out." How, as Mr Straw might have asked, had she got herself into this mess? "If you'd ever met my step-dad, you'd know I'm safer out here than I would be at home," she says.

Like me, she's only living rough in the daytime. When the hostel chucks her out each morning she's left to wander the streets and wait for it to open again. Unlike me, she spends her nights under a grey blanket in a scruffy Victorian building that reminds her of the care home she lived in briefly when she was a child. She is 35 times more likely to kill herself than me, according to a recent report from Crisis, and four times more likely than I am to die of "unnatural causes".

I explain to Jenny what I'm doing. I tell her about Jack Straw and John Gummer and how neither of them gave me any money, but one stopped, listened and offered some useful advice. Jenny's not very impressed, either with me or with them.

She doesn't want to be dependent on other people's charity, or their pity or their tangerines. She doesn't want to be in any articles about homelessness, she says, because they don't do any bloody good.

What Jenny and Mary and Britain's 400,000 other homeless people really want is for the next government to spare them some change in its first budget - so they can find homes of their own.