Ms McCann, whose daughter Madeleine, below, went missing four years ago from a holiday flat in the Algarve shortly before her fourth birthday, will join other mothers of missing children as she talks about the lack of emotional support available to families.
She will help explain the current state of support for families, saying they should be spared "the additional pain of financial and legal bureaucracy".
"When someone you love goes missing, you are left with unimaginable, unending heartbreak, confusion, guilt, and worry," she will say.
"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."
Ann Coffey, chairwoman of the all-party parliamentary group on runaway and missing children and adults, said the MPs were examining what "emotional, practical and legal support those families need to help them cope at such a traumatic time".
She said: "When a child or vulnerable adult goes missing the families left behind are absolutely devastated. Often the families feel isolated and alone."
Ms McCann, 43, will give evidence as Scotland Yard continues its review of the investigation into her daughter's disappearance in Praia da Luz on 3 May, 2007.
Last month, Ms McCann, from Rothley, Leicestershire, published a book about Madeleine's disappearance in a bid to revive efforts to find her daughter.
The official Portuguese inquiry into the disappearance was formally closed in July 2008, although private detectives employed by the McCanns have continued the search.
Ms McCann will be 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 20 May, 1992.
Ms Godwin said: "There are not the right words to explain how this emotional journey has evolved; it's been a long, slow and lonely task but after so many years I can usually keep painful emotions in a fairly secure part of me.
"I can now talk more freely about Q and our story and I can start to work with others in similar situations, although this interaction is both cathartic and difficult.
"I have learnt to gradually pull myself out of the emotional hole, accept the possibility of never seeing Q again, and accept the knowledge that I might never know the facts of his life or death. I have to honour his life whilst living with his and our loss."
Martin Houghton-Brown, chief executive of Missing People, said there was not enough support for families with missing children. He said: "As it stands, if your house is burgled you are automatically offered emotional, practical and legal support. If your child goes missing you may get nothing.
"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."
The MPs will also hear from Peter Davies, chief executive of the Child Exploitation and Online Protection centre and Home Office Minister James Brokenshire.
Vanished but not forgotten
CHEF Claudia Lawrence, 35, went missing on 18 March, 2009, from Melrosegate, Heworth, York. She sent a text message that night and was reported missing after she did not arrive for work the next morning. Claudia's father, Peter, gave evidence to the parliamentary inquiry in March.
Genette Tate was a 13-year-old newspaper delivery girl when she went missing from her home village of Aylesbeare, east Devon. It is thought she vanished shortly before 3:30pm on 19 August, 1978, only minutes after she had been speaking to two friends.
Andrew MacRae, three, went missing with his mother Renee on 12 November, 1976. After leaving her home in Cradlehall, Inverness, Renee dropped off her son Gordon, nine, at her estranged husband's house and drove towards Perth to visit her sister. They were never seen again.