"We've noticed a lot of individual grant applications coming in for beds," said Cushla McKenzie-Higgott, programme administrator at the children's charity Variety.
"That's something that we haven't really recognised as an issue before but now that we've noticed it, we're seeing it as a huge issue.
"Lots of kids sharing beds, sleeping on couches, lots of respiratory issues going back and forth."
The charity is now trialling a programme with its referrers, which requires healthcare workers to check whether children are sleeping in separate beds.
"It's just starting, but we're seeing a huge number of applications come in from Auckland and Northland," McKenzie-Higgott said.
In some instances the bed-sharing is cultural, because co-sleeping is common in Maori and Pacific families. But in most cases it is a symptom of families in hardship.
It is not limited to newborns or toddlers. Children up to 14 years old are sharing with another person as the winter cold bites and high rental costs make it difficult to afford basic items.
The most recent Child Poverty Monitor said 13 per cent of children in the lowest income households did not have a separate bed. A University of Otago study from 2013 indicates that the total figure is closer to 20 per cent.
Social Development Minister and Kelston MP Carmel Sepuloni said the statistics showed there was more work to be done in reducing overcrowding in New Zealand homes.
"In my electorate I've got one of the highest number of households where there are three or more families living in that household.
"As a consequence of that, you can imagine there are children that are sharing beds because of the fact that there's not enough space and they don't have a bed of their own."
Changes to welfare payments in July would gradually lift these people above the poverty line and assist with purchasing basic items, she said.
"All of us would like to see us get to the point where we no longer require the support of charities.
"But the reality is that we're not in this space at the moment, so we're grateful for the support of New Zealanders that offer up the charitable support that they do."
Because of rising demand, Variety has also decided to make its first public appeal this winter, rather than just seek further donations from existing sponsors.
It has a waiting list of 400 children, and the Herald is telling some of their stories this week.
Variety says a new bed costs around $237, and warm bedding is $118.
The families the Herald spoke to said their household budget was stretched by high and rising rents and medical costs, and did not extend to large one-off purchases.
Child Poverty Action Group economic advisor Susan St John said the role of charities like Variety had expanded in response to the breakdown of New Zealand's welfare state over the last two decades.
She said voluntary giving had its limits but charities were vital to many families' survival. However, charities could not replace properly-funded state support in the long run, she said.