Liberal Democrat leader Willie Rennie made the charge as he clashed with Nicola Sturgeon during First Ministers Questions at Holyrood today.
It came after a report published by the Scottish Government this week which stated the 12 week guarantee for all patients won't be met until 2021 - nine years after it was first introduced by the SNP.
Mr Rennie rounded on the Scottish Government's record on the issue today.
"The law states that patients will be guaranteed NHS treatment within 12 weeks," he said.
"This is the First Minister's law from when she was Heath Secretary. It was an SNP flagship law which helped them take power in 2007.
"And it's a law that the SNP Government has broken over 100,000 times.
"But on Tuesday the Government said they'd keep on breaking the law for another three years.
"If a member of the public was to break the law this many times they'd serve time in Barlinnie. Why is it that when the SNP Government breaks the law they think they can get away Scot-free?"
He added: "What exactly are the penalties for breaking this law that she has flouted so many times."
The First Minister accepted the breaches set out by Mr Rennie, but said 1.6 million patients had been treated within the legal timeframe.
"There are now fewer people waiting more than 12 weeks than was the case when this Government came to office,"
"The sanctions and steps that are taken when health boards don't meet the treatment time guarantee are actually laid down in the law. Willie Rennie can go and look, like anybody else, at what they are."
The legislation has no sanction for breaches of the law and is not legally enforceable. It states that NHS boards should seek to ensure treatment starts at the "next available opportunity" and give patients an explanation for the delay.