123,000 children across our country will go to sleep tonight without a place to call home.

For many of these children, the inside of a hostel, a B&B or even a converted warehouse is all that they have ever known. Together, they help make up 80,000 households that are trapped in the hidden world of temporary accommodation.

This isn’t just an injustice. It is a national scandal.

So I decided to visit the temporary accommodation in my constituency of Mitcham and Morden in South London to find out how children and their families are living.

I was puzzled. My map had taken me right into the heart of a working industrial estate. Lorries raced past me, builders were at work, and the operating machinery was deafening. A wall of waste surrounded the building and I could practically taste the toxicity in the air. Surely this could not be where over 100 children were living? Little was I to know the devastating conditions inside.

The rooms were so small that Anna was sharing a bed with her two young daughters and her newborn baby. They were all sleeping horizontally to fit in.

Then there was Amy, whose baby had a wheezy cough. The medical opinion pointed to the fumes he was inhaling.

And finally, Hannah, who had recently given birth in the industrial estate car park because the building was too remote for the ambulance to find.

These families are just some of the stories behind the statistics. But come to my advice surgery any Friday of the year and you will hear dozens of others. Because, since 2010, housebuilding has fallen to its lowest level since the 1920s, there are almost 200,000 fewer homeowners, incomes are rising slower than rents and rough sleeping has risen year on year.

We simply cannot keep writing more reports and willing more homes without finding the means to provide them.

So here are the means.

What do you think when you hear the words “green belt”? Presumably rolling fields and the phrase “green and pleasant land”. I certainly used to. The strength of the green belt’s brand means that questioning this perception brings about inevitable opposition and furore. And so it’s time to burst the myth that all of the green belt is actually green.

Let’s start with the car wash next to Tottenham Hale station (just a 13-minute train to King’s Cross). It was here that a housing association had its application to build new homes turned down due to the land’s ludicrous green belt designation – yet there’s not a single blade of grass to be seen.

Or let’s take the disused airfield in Wisley, Surrey. It was here that plans for 2,068 new homes were turned down on the basis that it has green belt status – but it is simply a barren mile of concrete. Hardly rolling fields…

Or how about the beautiful Whiteley Village in Hersham. It is home to 500 residents, all on limited financial means, and life here adding an extraordinary 5 years to a resident’s life expectancy. But yes, you guessed it, the village has this month lost an appeal to build just 60 more homes because this is designated Green Belt land. In whose interest, I ask?

Of course, I’m not referring to the genuinely green land – the areas of natural beauty, ancient woodland or our national parks. But I simply cannot understand why anybody would want to keep eyesores like waste plants, scrublands and chainlink fencing when our country is in such dire need of new homes.

Yet research shows that there are enough scrappy plots of so-called “green belt” land within just a ten-minute walk of London’s train stations to build one million new homes – and it would only take 3.7 per cent of the current green belt. It’s a proposal with backing from Parliamentarians, economists and thinktanks from right across the political spectrum.

Because no matter what the colour of your political party, the time for words is over and the time for actions is now.

There are 123,000 children relying on it.

Written by Siobhain McDonagh

Siobhain McDonagh is a Labour MP.