Complaints made by MPs to council bosses about adult social care and children's services are not always dealt with properly, claims a report.
County council bosses have admitted that instead of the complaints going through official processes, senior members of staff have been dealing with them directly.
It says the problem, which has become a "common theme", has meant the issues raised are not included in "lessons learnt reviews".
The matter was raised at a Lincolnshire County Council meeting.
The draft report said: "Some complaints were handled outside of the agreed statutory complaints process and bypassed the system and therefore were not logged, tracked, audited or included in lessons learnt reviews.
"Consequently, this also results in complaints not being adequately reported upon."
New proposals being put forward by Lincolnshire County Council would see processes put in place to ensure all complaints and council responses are formally recorded.
The report says the new system would allow for more "qualitative assessments" and consistent reporting of issues raised by MPs.
In 2011-12 there were 322 formal complaints received by the council.
Lincolnshire MPs say they have no objections to how the council has dealt with complaints.
The Conservative MP for Lincoln, Karl McCartney, said: "I have very cordial relations with all councillors as well as officers at the county council and have no complaints regarding how quickly or well issues we raise are dealt with."
Stephen Philips, Sleaford and North Hykeham's Conservative MP, agreed.
"I have to say that this is the first I have heard of it and that personally, I haven't had any problems dealing with LCC on any issue," he said.
"They are generally very efficient at addressing all my correspondence."