Police officers convicted of dangerous driving, a hit and run and public order offences are on duty in the county.
Figures revealed under Freedom of Information laws show 20 serving officers working for Lancashire Constabulary have a criminal record.
Of those seven were convicted and 13 were given a caution.
The majority are for motoring offences, including three for driving without due care and attention.
The most recent offence was a case of driving without due care and attention in 2013 where the officer was fined and given six penalty points in court this year.
Another officer was convicted in 2002 of failing to stop at the scene of an accident.
And an officer was convicted of a public order offence in 1983, the figures show.
Cautions were given for offences including assault, theft, shoplifting and an offence under the Dangerous Dogs Act.
A spokesman for Lancashire Police said: “Lancashire Constabulary expects good conduct and probity from its officers and staff at all times.
“Where wrongdoing is alleged, police officers are investigated and action taken as appropriate to each case.
“It should be remembered that there are more than 3,000 police officers in the county.
“It is very rare that a person with a criminal conviction will be recruited into the police service.”
In responding to the FOI the force said: “Many of the ‘convictions’ are cautions and did not therefore progress to court, and were issued before they joined the organisation.
“These cautions were declared by the officers at the required stages on their application and vetting forms when applying to work for the organisation. Assessments were carried out on a case by case basis for each officer before they were accepted into the Constabulary.
“Other incidents have taken place whilst officers were on duty (ie driving incidents). Allegations of a criminal nature will have been dealt with accordingly.
“Where appropriate they will have been assessed and reviewed by the CPS externally and Professional Standards internally.
“Once any criminal investigation has concluded, any subsequent misconduct matter would be addressed on the balance of probability.”