Unscrupulous practices by estate agents, including misleading surveyors about property prices and faking signatures, have been uncovered.
Reporters went undercover for four months at agencies
Agents put forward false offers to vendors and took backhanders, reporters for BBC One's Whistleblower found.
For four months they worked undercover in agencies in the London area. The firms involved are investigating the claims and have suspended staff.
It comes as the Office of Fair Trading launches a code of practice for agents.
Reporters Anna Adams and Emma Clarke went undercover to work in several estate agencies.
In the programme, some estate agents are shown to:
Deliberately mislead surveyors by lying about the value of other properties that have sold - this could result in buyers paying over the odds for a property
Fail to draw would-be tenants' attention to high fees and to lie to them about whether landlords would agree to break clauses in their contracts, resulting in them being tied into tenancy agreements for longer than they might otherwise have been
Fake signatures on documents
Sign up clients by tempting them with a high asking price for their property then, once "on their books", putting in false low offers to the vendors in order to encourage them to lower their price to a more realistic level
Put up "for sale" signs at properties not on their books - this is known as flyboarding and is illegal
Undervalue a property in order to sell it at a cheap price to a property developer in return for a cash backhander of £10,000
The programme also reveals that a firm of financial advisers - recommended to would-be buyers by a particular estate agents - passes supposedly confidential personal financial information back to agency staff so they know whether it is worth pushing clients to go for higher value properties than they really want to.
One estate agent supplied a reporter - posing as a would-be buyer - with a false British passport for £750 and false Customs and Revenue documentation, in order for them to get a mortgage.
The OFT is on Tuesday launching the Ombudsman for Estate Agents Company Limited's code of practice to try to ensure home buyers and sellers get a fairer deal when using the services of estate agents who are OEA members.
The OEA represents more than 40% of estate agency offices in the UK and deals with disputes between agents and buyers or sellers.
Whistleblower will be broadcast on BBC One on Tuesday, 21 March at 2100 GMT