Joanne and her husband Robert Wark lost their son Callum in March this year when a drunk Bulgarian lorry driver crashed into the 19-year-old on the A162 near Fairburn in North Yorkshire.
Callum died when his Renault Clio was hit by a Stoyan Andonov Stoyanov, a driver who was more than three times over the limit.
Within weeks Stoyanov was sentenced to seven years, with an expectation he will serve just half.
Callum’s parents have now brought their fight to parliament, with a call for a change in the law due before MPs.
Mrs Wark said she had still not adjusted to life without her only child, but that as the months went by it became clearer that something was wrong with the way the courts deal with those found guilty of death by dangerous driving.
She said: “The driver was handed the maximum sentence he was ever going to be given, he pleaded guilty early and the judge’s hands were tied in what sentence he could give.
“We were the lucky ones really, although it doesn’t feel that way, but we got the best sentence as the law stands.
“But it needs to be changed. When we walked into the court it was just 20 days after we lost Callum, we were expecting it to just be the start of the process.
“It was horrendous to be there but he pleaded and was dealt with there and then, with the judge telling us this is the best he could do.
“The system seemed to be built around the perpetrator, to deal with him as easily and as quickly as possible, and we think that could change if a judge was empowered to hand out stronger sentences in these cases.
“When you look at the sentences some people get or the amount of time that passes before they are free it shows the process is absurd.”
As Callum’s parents question the “disgraceful” sentencing guidelines, their fight for justice has gone before ministers.
Elmet and Rothwell MP Alec Shelbrooke used a House of Commons speech to call on the Government to address drink driving in its upcoming sentencing council review.
“Fewer than three in five drink drivers who kill receive a sentence of more than five years in prison,” Mr Shelbrooke told MPs.
“Justice is not about compensation, real justice is knowing that the killer of your only child receives a custodial sentence befitting of his crime. But more than that, justice should be about triggering change – a deterrent to prevent these terrible incidents happening to another innocent victim.”
He added that the law should be looked at to ensure foreign criminals who commit a serious crime are departed after their sentence.
“Under present deportation threshold criteria, non-EU nationals sentenced to 12 months or more are considered for deportation by the UK Borders Agency, whereas deportation is only considered for EU nationals who are sentenced for 24 months or over, unless they relate to drugs, sex, violence other serious criminal activity.
“This has to change.”