Kate McCann and Nicki Durbin. Photo / AP

The mother of a missing Auckland teenager has joined Madeleine McCann's mother in London, calling for support for families with missing children.

Sarah Godwin, whose son Quentin, 18, was last seen leaving his parents' Titirangi home in May 1992, said dealing with a missing relative "takes over your life".

She spoke to MPs in the House of Commons this week during the UK's first parliamentary inquiry into the rights of the families of missing people.

It consists of four sessions and is co-chaired by a cross-party panel of parliamentarians, who will make recommendations.

Mrs Godwin was joined by Kate McCann, whose daughter Madeleine, 3, disappeared from the family's holiday home in Portugal in 2007.

Also with the two women was Nicki Durbin, whose son Luke, 19, vanished four years ago.

The trio said there was a lack of emotional support and no legislation to protect the missing people "and the families left behind".

Quentin, who would be 37, moved from England to New Zealand with his parents when he was 2.

Mrs Godwin, who returned to the UK about 10 years ago, said her son could be anywhere, but was close to her parents in England, who have since died.

She told the BBC: "I think it's the connectivity that's really important for the families, or people who are struggling with a missing relative, not to have to search around and work out who to talk to."

Mrs Godwin, a fundraising consultant in Surrey, said Quentin, a former Green Bay High School student, left behind a letter that could be read as a suicide note, and the police stepped in and did "as much as they could".

"It just takes over your life, it becomes an all-absorbing and all-engrossing area of your life.

"You're driving down the road and you're looking at people walking up the street to see if you can see their faces, but it's the long term that's really the hard road."

Police and family scoured the bush, land and beaches looking for Quentin. Posters were put up in windows around the country and the family appeared on Crimewatch, pleading for information.

But there were no leads.

Kate McCann told the inquiry: "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.

"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."

Scotland Yard is reviewing the Portuguese investigation into her daughter's disappearance.

Mrs McCann said the chances of finding her daughter were greater because it had become involved.