Labour's Pola Uddin will not face criminal charges following allegations of expenses abuses, the director of public prosecutions has confirmed.
Keir Starmer, head of the Crown Prosecution Service (CPS), said in a statement there was not a realistic prospect of prosecution after claims that Baroness Uddin unfairly made 'night subsistence' claims.
Baroness Uddin said in a statement she was "relieved" that her "ordeal" had finally come to an end.
She added: "I only wish to say thank you to everyone who has supported me through this every difficult time and I now wish to turn back to my professional life and my public duties and my family."
Peers do not normally receive a salary, but are entitled to an allowance for night subsistence if they are based outside London. They qualify for this if their 'only or main residence' is not in London.
Although Baroness Uddin nominated a flat in Maidstone, Kent as her 'only or main residence' it was alleged her real 'only or main residence' was a house in east London.
A statement from the clerk of the parliaments which stated "ultimately it is up to members to designate an address as their main residence as they see fit" appeared to undermine prospects for a conviction.
Further clarification confirmed the threshold is that the 'only or main residence' must be visited at least once a month to qualify.
"On that interpretation, in any criminal proceedings, it would almost inevitably be necessary for the prosecution to prove, to the criminal standard, that any peer in question had not even visited the address they deemed their 'only or main' residence once a month," Mr Starmer explained.
"That presents a very real difficulty and we considered whether it would be open to the Crown Prosecution Service to advance a different definition of 'only or main residence' in any criminal proceedings. However, after careful consideration, we concluded that such a course would not be open to us."
Baroness Uddin became Britain's first Muslim peer in 1998.
She was the sixth parliamentarian to be investigated by the CPS. Its prosecution of three Labour MPs and one Conservative peer began in the courts yesterday, when Jim Devine, Elliot Morley, David Chaytor and Lord Hanningfield pleading not guilty to charges under the Theft Act.