The MP has two children with first wife Sonia Rossington, and two with second wife Karen Danczuk.
He is believed to have claimed thousands of pounds in additional expenses so he could accommodate them at a flat in the capital.
But questions have now been raised about how often the two eldest children actually stay with him.
Mr Danczuk has previously said he checked the claims with Ipsa and thinks he has done nothing wrong.
In a statement today Danczuk said: “My original claim was made properly and based on my honest interpretation of the Ipsa regulations.
“I maintain that the existing rules are poorly worded and not fit for purpose when it comes to modern families like mine.
“Some of my Parliamentary colleagues have approached me in the last week to say they agree with me on this point and that they have interpreted the rules the same way.
“I’ll be meeting with the chief executive of Ipsa about this and I will stress the need for the system to be more flexible to reflect the living arrangements of modern families.
“I am co-operating fully with the investigation and welcome the chance to get this matter cleared up.”
After Jeremy Corbyn won the Labour leadership, Mr Danczuk emerged as one of his most outspoken backbench critics.
But at the end of last year he became dogged by lurid headlines about texts he sent to Sophena Houlihan, then 17.
