Former Labour minister Denis MacShane has resigned after being suspended from the Commons for fiddling his expenses.
Chancellor George Osborne has appointed Mr MacShane to the post of Steward and Bailiff of the Three Hundreds of Chiltern.
The appointment is the technical procedure enabling MPs to resign their seat in the Commons.
Labour leader Ed Miliband said he was "right" to step down from Parliament after being condemned for abusing expenses rules.
The shadow home secretary said police were right to look again at whether former minister Denis MacShane's abuse of expenses broke the law.
Yvette Cooper said the case should be re-examined in the light of "very severe condemnation" by parliament's sleaze watchdog.
The comments came after the Commons authorities insisted that damning letters from Mr MacShane to the standards commissioner could not be used against him in court.
Senior officials say they are protected by parliamentary privilege because they were collected during proceedings of the House.
It has been revealed that letters from former minister Denis MacShane admitting expenses abuses cannot be used to prosecute him because they are protected by Commons rules.
Officials said parliamentary privilege meant the key correspondence was withheld from police when they launched a probe into the MP two years ago.
And the documents are still not legally admissible - even though they were published in a Commons sleaze report today.
It is understood Denis MacShane formally applied for the post of Crown Steward and Bailiff of the Chiltern Hundreds tonight - the traditional way of resigning from the Commons as there is no way for MPs to resign.
Chancellor George Osborne is expected to confirm his appointment tomorrow, at which point he will cease being an MP.
A Metropolitan Police spokesman said the force would now consider the contents of the Commons report.
He said: "We are aware of the report and will be assessing its content in due course."
A senior Labour source told PA that; "Denis has done the right thing."
The former Europe minister said he wanted to take "responsibility for my mistakes" after the Standards and Privileges Committee recommended he be suspended without pay and pension for a year - the longest suspension of an MP in living memory.
I have been overwhelmed by messages of support for my work as an MP on a range of issues but I accept that my parliamentary career is over.
I appreciate the committee's ruling that I made no personal gain and I regret my foolishness in the manner I chose to be reimbursed for work including working as the Prime Minister's personal envoy in Europe.
Denis MacShane tonight announced he was resigning as an MP after the Westminster sleaze watchdog found he had wrongly claimed thousands of pounds in expenses.
– Labour party statement
These are very serious findings concerning Denis MacShane and we accept his statement this morning that his career as a Labour MP is effectively over.
In the light of the report's recommendations to the House, the Labour Party has suspended Denis MacShane with immediate effect, pending a full NEC (National Executive Committee) inquiry.
We will be talking to Denis MacShane about his future and the best course of action for him and for his constituency.