More than 24,000 people are faced with sleeping rough on the streets or spending their nights in tents or on public transport, new research shows.
The number has increased massively over the past five years, according to the national homelessness charity Crisis, which commissioned the study from Heriot-Watt University in Edinburgh.
Crisis chief executive Jon Sparkes said: Christmas should be a time of joy but for thousands of people sleeping rough, in tents or on public transport, it will be anything but.
While most of the country will be celebrating and enjoying a family meal, those who are homeless will face a struggle just to stay safe and escape the cold.
The research shows 12,300 people are currently sleeping in the streets and nearly 11,950 are spending their nights in cars, on trains, on buses or in tents.
It found that between 2012 and 2017, these numbers increased by 120% in England and 63% in Wales – but the numbers fell by 6% in Scotland.
Crisis says people sleeping rough in England is more than double what government statistics suggest.
The charity said the study pulled together a range of sources, including data from support services that record peoples experiences of sleeping rough which, according to the researchers, is not included in the governments count.
The charity said those sleeping outside are subject to a range of dangers, with homeless people almost 17 times more likely to be victims of violence and 15 times more likely to be verbally abused.
Crisis said it wants national and devolved governments to tackle the root causes of rough sleeping by strengthening the welfare system and making sure every homeless person has access to mainstream housing as quickly as possible.
It is also asking the public to help by calling support services if they find someone sleeping rough, and by raising funds for both its year-round services and its Christmas centres.
Mr Sparkes continued: This situation simply cannot continue.
While the Scottish Government has taken the first step in announcing a plan to eradicate homelessness, full implementation cannot come soon enough.
Meanwhile, the governments in England and Wales must step up urgently with their own plans to end this crisis.
We know homelessness can be ended. Earlier this year we set out the exact government policies that would end homelessness across Britain.
Our research shows that with these policies in place, homelessness could be ended in just 10 years.
Housing and homelessness minister Heather Wheeler said: It is simply unacceptable that anyone has to sleep on the streets which is why we have set out bold plans backed by £1.2 billion to tackle all forms of homelessness, including our £100 million Rough Sleeping Strategy.
This is already making a difference through additional bed spaces and support workers and new legislation means people at risk are getting the help they need more quickly.
But we know more needs to be done to end rough sleeping for good and are committed to work with partners like Crisis to do just that.
Campaign director at Shelter Greg Beales said: This is a really important piece of research that shows how the official rough-sleeping statistics are likely to be way off the mark.
The government must address the deep problems in our housing system that are leading to homelessness – fixing the problems in the welfare system and committing to a major social house-building programme.