Housebuyers are being encouraged to break the law in order to obtain huge mortgages, the BBC has discovered.
Brokers, and even banking staff, have been telling buyers to lie about their incomes to get bigger and bigger loans.
But what many don't realise is that they could end up in jail.
And these underhand tactics could also be the reason why house prices have gone on rising for so long.
On Monday, the mortgage lender Birmingham Midshires suspended three mortgage advisers while it investigates allegations that customers had been encouraged to exaggerate their salaries on application forms.
The company, owned by Britain's biggest lender HBOS, has also suspended sales of so-called "self-certification" mortgages, where borrowers certify their own incomes without the need to supply payslips.
The allegations have been made by the BBC's Money Programme, which will be screened on Wednesday evening.
The programme also makes similar allegations about advisers at or recommended by several of the UK's biggest estate agent groups.
Several mortgage advisers are quoted boasting about how easy it is to get away with the mortgage fraud.
Tony Shaw QC, a criminal lawyer specialising in serious fraud, told the Money Programme: "A person who fills out a form, knowingly entering a false statement about his income or his occupation is at risk of going to prison.
"It is a serious offence."
Mortgage brokers who advise borrowers to lie could also face severe penalties.
"We will not tolerate any behaviour that might compromise our brand," said Dan Watkins, managing director of Birmingham Midshires.
"That is why we have taken the actions that we have announced today."
HBOS chief executive James Crosby declined to talk to the Money Programme.
Desmond Fitzgerald, an expert in financial markets who advises financial institutions and regulators, suggested that fraudulent mortgage applications might be a factor behind continued high property prices.
"Over the past two years, most forecasters including myself expected the housing market at best to stabilise and more likely to fall. Instead it's powered ahead.
"Now clearly if there is this extra flow from these fraudulent self-certified mortgages, that will push hundreds of millions of extra cash flow into the housing market.
"So you get this sort of self-feeding frenzy, a real bubble effect."
Mr Fitzgerald said people who had obtained mortgages through fraud also risked financial ruin because they could end up paying more than half their after-tax income in mortgage repayments.
"A lot of people would find that difficult, if not impossible to manage," he said.
The Money Programme will be shown on Wednesday 29 October at 1930 GMT on BBC Two.