Partnership with an estate agent has allowed the charity to highlight the UK's great housing divide.
An estate agent is advertising some of London's most squalid properties in its shop windows in support of a new campaign by Shelter.
Douglas & Gordon is showing images of boarded-up bungalows and disgusting bathrooms alongside £2m properties in 13 branches across leafy south-west London.
The spoof ads, which are also being displayed on the company's website, are designed to prick the consciences of wealthy homebuyers and sellers into supporting the homelessness charity.
The adverts mark the launch of Real Homes, a year-long Shelter campaign created to tell people about the widening housing divide between rich and poor, as well as to raise money for the charity.
The campaign has unusual origins - the idea was conceived not by Shelter but by the advertising agency Leo Burnett.
An employee at the firm designed a spoof estate agent's advert highlighting the problem of homelessness. "We thought it would be great if it could contribute to something more than winning an award," said Jim Thornton, executive creative director at Leo Burnett.
Thornton showed the advert to his Suffolk neighbour, Ivor Dickinson, who is managing director of Douglas & Gordon. The two then approached Shelter with the idea of using the ads as part of their campaigning.
"It's incredibly brave of Douglas & Gordon to do this," said a spokesman for Shelter. "If it had wanted to play safe, it wouldn't have touched it. It shows that it wanted to give something back."
The estate agent has contributed £25,000 to the campaign and will be asking customers to make donations.
"If we're ever going to prick someone's conscience, it will surely be when they have just sold their house for £1m," said Dickinson.
"I was nervous about doing it and no doubt it will shock some of our clients, who will be upset at seeing their £2m property alongside squats.
"So far, however, the response has been amazing. Estate agents have a dreadful reputation - when people see us doing something like this, they really notice it."
Adam Sampson, director of Shelter, said: "When a company such as Douglas & Gordon is prepared to send a message to its consumers in such a potentially controversial way, we have a much better chance of showing that an unmanageable gap has emerged between those at the top and the bottom of the housing ladder."
- Spoof ads showing some of London's most run-down properties are being advertised in an estate agent's windows
- The ads, created by an employee at the advertising agency Leo Burnett, have been designed to shock people into realising there is a growing divide between those at the top and those at the bottom of the housing ladder
- They encourage people to donate to Shelter's new Real Homes campaign, which will last for a year
- A spokesman for the homelessness charity has praised the estate agent, Douglas & Gordon, for an "incredibly brave" gesture showing that it wanted to "give something back".