Image caption Squatters moved into houses owned by film director Guy Ritchie earlier this year

For many people, the word squatter conjures up the image of a dreadlocked, middle-class, tree-hugging hippie eking out an alternative lifestyle in someone else's home. But with plans afoot to outlaw squatting, just who are today's squatters?

"I don't feel I am freeloading. I am using something that was going to waste."

Biz is a 24-year-old arts graduate who is squatting in a house in Bristol. She used to work in a bar but she could not get enough shifts to cover the rent. She is not claiming benefits and is earning a bit of cash by helping build furniture for a school's playground.

With the government consulting on a proposal to criminalise squatting, one of the big issues will be defining just who squatters like Biz are.

Many people's idea of squatters will be gleaned from media reports of young people occupying multi-million pound houses in the UK's most exclusive postcodes. Less frequently, there will be sensational stories about owners returning from holiday to find squatters in their house.

Squatting laws Squatting is when someone occupies an empty or abandoned property which they don't own or rent, and without the owner's permission

This kind of squatting is not currently a criminal offence in England, Wales and Northern Ireland and is dealt with by the civil courts

Squatting has been illegal in Scotland since the mid-19th Century

The police will get involved if a squatter has made someone homeless, has broken into the property or has caused damage while staying there

The predominant media image is one of posh, anti-establishment eco-warriors who spend their rent-money on parties and devote their energies to sustainable living. The counter-argument from squatters is that they often endear themselves to neighbours by fixing up derelict properties and establishing cafes, art galleries and workshops in their new homes.

But what is the reality?

Organisations and campaign groups such as Crisis, Squash and the Advisory Service for Squatters say a significant number of squatters are homeless individuals and families, many of whom have mental health and addiction problems in addition to not having a roof over their heads.

Opponents of the proposed criminalisation say it will hit the most vulnerable people in society at a time of government cuts and rising household bills.

They claim the beneficiaries will be people who own commercial premises and leave them empty for financial gain, such as tax avoidance or property speculation. They also say it will burden the police and justice system.

Chris Town, landlord in Leeds and York A tenant gave notice to quit and I went around to collect the keys from him. He was still there and there was another chap. I thought he was helping him move but he claimed squatters' rights and refused to leave. My instant reaction was to go to the police who told me it was a civil matter unless the chap had broken in, but he had been invited in. I felt helpless. I found out from the police and my lawyer that if the squatter left I could go in and make it secure and that's what I did. I had to stake the property out and wait until he went out. It cost me about £1,000 and I lost rent. *Chris Town is vice chairman of the Residential Landlords Association

But there are other people who argue that squatters are rent refuseniks.

Mike Weatherley is the MP for Hove and Portslade, a squatting hotspot, and he says it is a "myth that homeless people and squatters are one in the same".

"For a lot of people squatting is a lifestyle. They move from property to property and are often anti-government, making some kind of protest statement. It is those people we have to stop."

He says the squatters are often well organised and well aware of their rights, and many engage in anti-social behaviour such as drug taking and fly-tipping.

There are no official figures for the number of squatters, let alone a breakdown of their age, location or educational background. While London stands out, by virtue of its sheer size, squatting is also an issue in many other cities including Bristol and Brighton.

The government estimates there are 20,000 squatters in the UK but squatting groups say the real total is more.

Squash, Squatters' Action for Secure Homes, points out that the number of people on local authority housing lists has nearly doubled since 1997 to five million and there are an estimated 650,000 empty properties in the UK.

Jason, squatter in Hampstead, London I am from Latvia and have been squatting for a year-and-a-half. I am not working and don't have the means to pay rent. I didn't think I would be doing it for so long. It is not the lifestyle I would chose. In the beginning it seemed cool but in practice it's difficult. Many of the people who chose this lifestyle are suffering from personal issues. For some it is like a substitute family. For me, it is just a way to live rent-free. The building is not in good condition but we have fixed the roof which was leaking and cleared the garden. I am going to leave London and find a job, maybe Newcastle.

Reuben Taylor, from Squash, says these places can provide for some of the most vulnerable people in society, such as homeless people, former prisoners and those with addiction or mental health problems.

"They are the majority of people who squat but they do so very quietly."

Crisis, the national charity for single homeless people, carried out a study this year which suggested 39% of homeless people had squatted at some time.

Katharine Sacks-Jones, head of policy at the charity, says squatting is another form of homelessness, especially as some squats are in "horrendous" conditions.

"A lot of the debate is coloured by the so-called lifestyle squatters but this is very far from the reality for vulnerable homeless people who don't have another option."

The UK has a long history of squatting. In feudal times, if a house could be erected between sundown and sunrise the occupants could claim the right to tenure and could not be evicted.

Squatting was a big issue in the Peasants' Revolt of 1381 and again for the Diggers in the 17th Century. Founded by the anarchist Gerrard Winstanley, they were peasants who cultivated waste and common land, claiming it as their rightful due.

After World War II, squatting was a necessity for some and people slept in all sorts of buildings. The next wave came in the 60s and 70s and while the country was in the grip of another housing crisis, there was also a cultural move towards trying out a different style of living.

Types of squatters Deprivation-based - eg homeless people

Alternative housing strategy

Entrepreneurial - eg setting up a cafe and serving the community

Conservation - preserving buildings

Political - as a form of protest or to create a social centre *From Dutch sociologist Hans Pruijt

Professor Lorna Fox O'Mahony, an expert in property law, says there are three factors associated with spikes in urban squatting - rising house prices, a high proportion of empty homes and an increase in the homeless population.

"The rise in urban squatting in the 60s and 70s was largely focused around council properties. Houses were lying empty rather than being allocated."

She says a rise in the mid-2000s was also linked to rising house prices and a lack of affordable housing, particularly in the South East of England.

Prof O'Mahony says as more and more people became home owners, they became increasingly upset by squatters.

"People were paying mortgages and were horrified that people weren't paying their way."

Groups such as Crisis and Squash are warning that squatting may become the only option for more and more people as cuts to housing benefits and other front-line services start to bite.

Biz in Bristol says she will be homeless if squatting is criminalised, as will her 12 squatmates, some of whom are students who cannot afford to rent and people who are looking for work.

She says she will continue to squat until she finds a job that she not only loves but which also pays the rent. Though she admits she will probably be evicted before that happens.