The Lords Commissioner for Standards has confirmed receiving a letter from Baroness Warsi, in which she asked him to investigate her expenses.
A spokesman for Paul Kernaghan said:
The Commissioner has received a letter from Baroness Warsi asking him to look into the allegations against her.
We have also had indications from a third party that they will write and complain, but we haven't received that yet.
The Commissioner has to do an initial assessment of the allegations and check whether it falls within his remit and see if it needs further investigation.
If it does he will launch a formal investigation, but we aren't at that stage yet.
It is understood that the third party mentioned is Labour MP John Mann, who said he would write to the Commissioner.