Letters written by former Rotherham MP Denis MacShane in which he allegedly admits fiddling his expenses cannot be used to prosecute him.
They're protected by parliamentary privilege, so were withheld from police when they launched a probe in to the MP two years ago. Prosecutors are still not legally able to use them.
Dennis MacShane resigned as an MP on Friday after it was found he submitted nineteen false invoices over a four year period.
The co-chairman of the Conservative Party Baroness Warsi has been cleared of allegations she wrongly claimed Parliamentary expenses.
It was alleged the Dewsbury-born peer had claimed overnight expenses for staying in London while living rent-free at a friend's house.
An official investigation has now exonerated her.