Nothing protects the families of missing people left behind, Kate McCann has said.
Mrs McCann, whose daughter Madeleine went missing from her family's holiday flat in the Algarve shortly before her fourth birthday, joined other mothers of missing children as she talked about the lack of emotional support available to families.
Calling for the Government to show its support, Mrs McCann said there was "currently no legislation to protect missing people and their families left behind".
Speaking outside the Commons while holding up a picture of Madeleine, Mrs McCann said: "If your house is burgled, you are automatically offered victim support with emotional, practical and legal assistance.
"If your child goes missing, you may get nothing.
"This parliamentary inquiry has the potential to change that."
She went on: "When someone you love goes missing, you are left with unimaginable, unending heartbreak, confusion, guilt and worry.
"In addition to the reassurance that everything possible is being done to find their missing loved one, families need support. And they should be spared the additional pain of financial and legal bureaucracy."
Mrs McCann, 43, issued her appeal to the Government as Scotland Yard continues its review of the investigation into her daughter's disappearance in Praia da Luz on May 3, 2007.
Last month, Mrs McCann, from Rothley, Leicestershire, published a highly-personal book about Madeleine's disappearance in a bid to revive efforts to find her daughter.
The official Portuguese inquiry into the disappearance was formally shelved in July 2008, although private detectives employed by the McCanns have continued the search.
Mrs McCann was joined by Sarah Godwin - whose son, Quentin, was 18 when he went missing in New Zealand while on his way to an after-school job on May 20, 1992 - and Nicki Durbin, whose son, Luke, 19, went missing four years ago.
The three mothers, each holding images of their missing loved ones, faced the press ahead of the first session of the inquiry.
Martin Houghton-Brown, chief executive of Missing People, said: "From dealing with finances, insurance policies, bank accounts and mortgages through to having a missing person declared presumed dead, families left behind often struggle to deal with institutions that have no system for their clients going missing.
"This inquiry is a landmark opportunity for parliamentarians to ensure that families are able to access the full range of support that they so desperately need."
Mrs McCann told the MPs she did not think it should be left to "grieving parents" to search for their child.
"I don't think this should be the role of grieving parents," she said.
Mrs McCann added that this was compounded by a "lack of communication and information".
Calling for a single point of contact between the families of missing people and the police, Mrs McCann said: "To be left in the dark when your child is missing and at risk is unbearable."
Human beings are not equipped to deal with such ordeals and more support is crucial if "families are to survive".
She went on: "Many people have been worn down by this process because it's absolutely relentless and exhausting."
But she added that now Scotland Yard was involved, "I feel the chances of her being found are improving".
Mrs McCann said that, despite being medically trained, she simply "could not function" when Madeleine went missing.
"It was the first time in my life when I felt out of control," she told the MPs.
Counselling had helped "to talk, to vocalise our fears and to challenge our fears", she said.
Ms Durbin also spoke of her "terror" at hearing about the discovery of a decapitated body on the local news, fearing it was her son, but not having anyone to call to find out more.
A point of contact with the police was crucial, she said.
Her son went missing after a night out in Ipswich in 1996, she told MPs.
Prime Minister David Cameron's official spokesman said help for families of missing people was "certainly a priority for the Government".
The spokesman said: "We are working hard to ensure that we have the best arrangements in place to support families when a loved one goes missing.
"From July this year, the Child Exploitation and Online Protection Agency will be taking over responsibility for missing children, with the aim of further improving the service that families receive."
Mrs McCann added: "The sense of helplessness you feel is overwhelming."
Home Office Minister James Brokenshire, who also gave evidence to the inquiry, said: "We are acutely aware of the pain caused when a loved one goes missing and we are working hard to ensure the best arrangements are in place to support families.
"We continue to work closely with the voluntary sector, providing additional funding for the valuable work of the charity Missing People, which provides a lifeline to missing people and their families through its helpline and wider support services."
He went on: "From July 1, the Child Exploitation and Online Protection agency will take over responsibility for missing children, further improving the service that families of missing children receive, and providing further specialist support to police forces in missing children cases."
Mr Houghton-Brown told the MPs that up to 20,000 families a year could benefit from the support provided by the Missing People charity, but many were unaware that that help was there.
He called for police forces to let the families of missing people know that the charity was there and some support was available.
"I would rather face the reality that 20,000 families at least know the support is there and available than know that what happens at present is we have scenarios like we have heard this morning where families don't even know that support exists," he told the MPs.
Chief Constable Nick Gargan, chief executive of the National Policing Improvement Agency (NPIA), said: "There wouldn't be a police officer in this country who wouldn't change the way they deal with missing persons if they'd listened to the evidence session I've just listened to."
MPs heard how families often felt they were being a nuisance to officers, felt they were treated as if they were wasting police time, and were left in the dark by police.
Forces receive 356,000 reports relating to 200,000 missing people each year - the equivalent of one report every 90 seconds, Mr Gargan said.
Up to 80% of these return home within 24 hours.
But between eight and 35 people are found dead each week after being reported missing, he told the MPs.
Of those who went missing, 52% were male, 48% female and two in three were young people aged under 18, he said.
Assistant Chief Constable Phil Thompson, the lead on missing adults for the Association of Chief Police Officers (Acpo), said: "This is crying out for a national strategy for missing people."
There is currently "a significant amount of clutter in this world" and the Acpo guidance is not as accessible to police officers as it should be, he said.
"That isn't working well enough and we have to do better."
Mr Thompson also apologised for the officer who accused Ms Durbin of wasting police time.
She told the inquiry that an officer once told her that, once her son turned up, the police would explain to him how much time and resources he had wasted.
Luke Durbin is still missing.