The MPs' expenses scandal resulted in serious damage to Parliament's reputation and reduced confidence in "our priceless democratic system", Court of Appeal judges said today.
Their comments came as they refused to reduce the 18-month prison sentence imposed on former Labour MP David Chaytor for fiddling his parliamentary expenses.
It had been argued on behalf of 61-year-old Chaytor, a former lecturer, of Lumbutts, Todmorden, West Yorkshire, that the appropriate sentence in his case was one of 12 months.
Rejecting his plea, the Lord Chief Justice, Lord Judge, sitting in London with Mr Justice Henriques and Mr Justice Foskett, said: "This was a grave breach of trust and there was a further aggravating feature of this case.
"It is difficult to exaggerate the levels of public concern at the revelation of significant abuse of the expenses system by some Members of Parliament.
"Some elected representatives, vested with the responsibility for making the laws which govern us all, betrayed the public trust."
He added: "There was incredulous consequent public shock.
"The result was serious damage to the reputation of Parliament, with correspondingly reduced confidence in our priceless democratic system and the processes by which it is implemented and we are governed.
"This element of damage caused by the appellant and others cannot be valued in monetary terms, but it is nonetheless real, and the impact of what has been done will not dissipate rapidly."
Chaytor, who forged tenancy documents and invoices to falsely claim more than £22,000 of taxpayers' money for rent and IT work from the Commons authorities, was jailed on January 7.
Lord Judge said of Chaytor: "This sad fall from grace was entirely self-inflicted."
He added: "As a Member of Parliament, the appellant was entitled, within prescribed rules, to claim for expenses incurred by him in the course of fulfilling the responsibilities of his office.
"The rules are set out in a document known as the Green Book, published by the House of Commons Department of Resources, which was also responsible for the administration of the expenses claims system."
Lord Judge said: "Until what became known as the 'expenses scandal', it was an essential feature of the operation of the scheme that Members of Parliament were invariably treated as honest, trustworthy people and the unwritten assumption was that only claims for expenses genuinely incurred in accordance with the rules would be made."
Chaytor was guilty of "serious dishonesty".
His good character was destroyed "and his public life has been shattered".
The judge said: "He has publicly admitted his dishonesty and his humiliation is complete."
Chaytor prepared and submitted false documents, knowing they were false, "to sustain fraudulent claims for expenses".
Lord Judge said: "The loss to the public purse was significant."
Chaytor initially denied the charges but changed his plea after failing to have the case thrown out citing parliamentary privilege and that he could not receive a fair trial because of media scrutiny.
He pleaded guilty to three counts of false accounting between November 2005 and January 2008.
The fraud involved bogus documents he submitted to support claims totalling £22,650 for IT services and renting homes in London and his Bury North constituency.
London's Southwark Crown Court heard that he received only £18,350 because he had already reached his limit for the IT expenses and was not awarded the full amount for one rental claim.