A Preston police officer used Lancashire Constabulary computer systems to run searches on his would-be neighbours before deciding whether to buy a house.
The alleged misuse of police systems happened last year while the officer, a police constable, was deciding whether to buy a property in Tarleton, near Preston.
He is said to have run checks on residents in the street to check whether they were on the system.
It is one of dozens of investigations launched by Lancashire Police between 2008 and 2010 for alleged breaches of data protection – most to do with officers misusing police computer systems.
In another incident last year, a PC from the force’s northern division, which covers Lancaster, Morecambe and Wyre, was accused of using the systems to check the criminal past of his daughter’s husband.
He found that he had a conviction for sexual offences and told his daughter and someone else, it was alleged.
Today Lancashire Police said the misuse of computer systems “would not be tolerated” and they would always take “robust action” against officers who insist on breaching the public trust.
Other breaches of the systems include officers running criminal checks on their own families and by one officer to find out where his ex-wife and her current partner were living.
In another incident in Fylde, an officer passed information about a man to his sister, who then used it against him in a letter about his children.
The findings were revealed by the force under the Freedom of Information Act.
Six officers have resigned over the breaches and a further 12 have been sacked. Many others have been given oral or written warnings.
A police spokesman said: “Lancashire Constabulary expects the highest standards of professional behaviour from all employees in relation to information security.
“The public rightly expect that we maintain the security and integrity of all information held on police databases and it is paramount that we maintain their confidence in our ability to do so.
“We audit how our staff access information to ensure that it is for policing purposes and that they are using that information lawfully and appropriately.
“The misuse of police systems by any individual staff member will not be tolerated as it is recognised that this can have a negative impact on public confidence.
“The force will always take robust action to investigate when necessary and anyone found to have breached the expected standards of behaviour may face criminal or misconduct proceedings.”