He was speaking after a court judgement in the case of Poppi Worthington.
On Tuesday a family court judge ruled Paul Worthington carried out a "penetrative" attack on his daughter.
Home Office minister Karen Bradley said no action could be considered until after a second inquest had taken place.
Mr Worthington, 48, who denies any wrongdoing, cannot face criminal action unless new evidence emerges.
Read more on this and other stories on our Local Live page.
Sir Simon said the authorities must now "look again" following the ruling by High Court family judge Mr Justice Peter Jackson, which was made on the balance of probabilities.
The former Liberal Democrat MP told BBC Radio 4's Today programme the "very fact" the judge had made the findings public "must give cause for the authorities who deal with criminal matters to look again at the evidence".
Sir Simon said "justice demands" the original decisions in the criminal investigation be reviewed and he called for the Crown Prosecution Service (CPS) to reopen the case.
He said: "I'm sure they will review the case, I'm sure that is the right thing that should happen.
"If the justice system is about not just justice for the deceased but to make sure that the welfare of the children who are still alive is best looked after, then it must be in the interests of justice that there is a review now as to whether there was any criminal liability for anything that led to the death of this poor little child."
The BBC's legal affairs correspondent Clive Coleman
There are some important legal distinctions involved in this tragic case.
Mr Justice Peter Jackson made his finding that Paul Worthington assaulted his daughter on the civil standard of proof. That standard is "the balance of probabilities", in other words that it is more likely than not Paul Worthington carried out the assault.  A finding in a civil court to this standard falls far short of a finding of guilt in a criminal case and should never be confused with it.
The Crown Prosecution will charge a suspect with a crime and bring a case to court if there is a "realistic prospect" of a criminal conviction.  That is similar to a "balance of probabilities" test in that it also means the CPS regard the evidence as making it "more likely than not" there will be a conviction.
So, based on Mr Justice Jackson's finding, why should a criminal case not be brought? There is further important and subtle distinction. The CPS must consider whether there is a realistic prospect of a jury convicting on the higher criminal standard of proof, i.e. beyond a reasonable doubt or satisfied so that they are sure.
Applying that test to the evidence, the CPS decided there was not a realistic prospect of a conviction.  Following the Family Court proceedings there will be a second inquest into Poppi's death.  If new evidence comes to light, the CPS will reconsider its decision.
Poppi collapsed with serious injuries at her home in Barrow, Cumbria, in December 2012 and was taken to hospital where she was pronounced dead.
Cumbria Police conducted no "real" investigation for nine months, Mr Justice Jackson found, as senior detectives thought a pathologist "may have jumped to conclusions" in her belief the child had been a victim of abuse.
The toddler was buried in February 2013, precluding a further post-mortem examination, after her body was released by the local coroner.
There is now said to be an "absence of evidence" to find out how Poppi died, or definitively prove if or how she was injured.
The death of the toddler had been shrouded in secrecy, with a 2014 fact-finding civil court judgement being kept private so as not to prejudice any criminal proceedings.
John Woodcock, Labour MP for Barrow, said he felt "sick and angry about the failures from social services and the police which have meant that poor Poppi Worthington has not had justice for her death".
He told the BBC's Victoria Derbyshire programme: "I want the home secretary to step in now and give this case to another force to try to salvage some hope that there could be a criminal investigation after all of the failings."
Last month, three medical experts gave evidence in open court stating they disagreed with the findings of Home Office pathologist Dr Alison Armour, who believed Poppi was the victim of "a penetrative sexual assault".
Mr Worthington was arrested in August 2013 and questioned on suspicion of sexual assault but was not charged with any offence.
The CPS has previously said it conducted "a thorough review of the evidence" but decided it was insufficient to provide a realistic prospect of conviction.
Responding to an urgent House of Commons question on the issue, Ms Bradley said "The attorney general has granted a second inquest and until that inquest is completed, we will not have the full facts.
"In order for the case to be reopened, new evidence will need to come to light, which may or may not be the case depending on the IPCC inquiry and also the second inquest."
A criminal investigation into a father found to have sexually assaulted his 13-month-old daughter shortly before her sudden death must be reopened, ex-justice minister Sir Simon Hughes says.