Liberal Democrat Alistair Carmichael, who was previously a prosecutor and a defence lawyer, said the scheme, which means burglars who break into homes over the festive period face five times the usual jail sentence, seemed like little more than a politically-inspired stunt.
As policing and the justice system are devolved to Holyrood, Carmichael, as a Westminster politician, has no influence over the issue. However, in a Sunday Herald interview, he was scathing about the new scheme, suggesting it was the product of meddling by SNP ministers.
Unveiled by the police and Crown Office last week, the scheme will see housebreakers taken down a tougher prosecution route for offences committed between December 16 and January 6.
Instead of the usual maximum sentence of a year, festive burglars face up to five years behind bars.
Scotland's second-highest prosecutor, Solicitor General Lesley Thomson QC, said the increase was intended to send "a strong deterrent message".
Alex Salmond praised the approach at First Minister's Questions on Thursday, when he was asked why it would not apply all year round. "The sentence is for the determination and judgment of the court, but I would have thought most people would welcome the initiative from Police Scotland and the Crown Office to address a problem that has been identified," he said.
Carmichael savaged the scheme, saying prosecutions were supposed to be based on a range on evidence, not just the date.
"I don't know whether I should laugh or cry. I was a prosecutor, I started in the Crown Office. Every case was decided on its own merits.
"For a housebreaking you would look at the record of the accused, you would look at the manner in which the housebreaking was undertaken, the effect on the victim, the value of the goods that were taken, whether it was part of a course of conduct, [as] most housebreakers are serial offenders.
"To trump all these serious, important considerations with a single issue, which is what date did this happen on, is ludicrous. Procurators fiscal must just be wondering if this is a policy for April 1, not December 25."
Housebreaking is normally prosecuted on summary complaint or indictment, with summary cases carrying a maximum jail sentence of a year. Last year the average sentence was 265 days.
But this Christmas there is a presumption that all housebreaking and attempted housebreaking will be prosecuted on indictment, meaning the sentence could be five years if the case goes before a sheriff and jury or to the high court.
Human rights lawyer John Scott QC warned the crackdown could end up generating appeals, as criminals could argue is was unfair.
Carmichael added: "You see this from time to time. You will find that, usually as a result of political pressure, some gimmick is produced in prosecution policy, and this sounds like a gimmick of the worst sort."
He also predicted courts would refuse to impose tougher sentences just because of Christmas.
A Crown Office spokesman said: "By prosecuting on indictment, we are making the five-year sentence available. Ultimately it is for the courts to decide on the circumstances in each case what the appropriate sentence should be."