Christian charities are among those calling on the next Mayor of London to tackle homelessness in the capital. 

Housing Justice and the West London Mission are among more than 20 charities who have called for the new Mayor who will succeed Boris Johnson after elections in May to do more to help rough sleepers.

Last year at least 7,500 people slept on the streets of London and tens of thousands more are technically homeless, housed in hostels and elsewhere. Latest figures show that 2,862 people were found sleeping rough in London in the last three months of 2015, an increase of 12 per cent on the same period last year.

More than 1,500 people have already signed the petition  organised by the charity Crisis. A new report by Crisis and the Joseph Rowntree Foundation this week found that local authorities across England are struggling to cope with rising numbers of single homeless people. The report says that nine out of 10 English councils find it difficult to help single homeless people aged 25-34, while nearly as many find it difficult to help people aged 18-24.

As many as 275,000 cases of homelessness were recorded nationally in the past year, many of them involving families with young children. The Lead London Home manifesto states: "Homelessness is a devastating experience with significant impacts for an individual's health and wellbeing. Mental and physical health problems can be caused or exacerbated by rough sleeping. Homelessness is also dangerous, with homeless people 13 times more likely to be a victim of crime than the general public. Shockingly, the average age of death for a homeless person is just 47 – 30 years younger than the national average."

Even in the 21st century, homeless people who ask their council for help can still be turned away to sleep on the streets, the manifesto says, because most single homeless people are not considered to be a "priority", meaning the local council has no legal duty to find them housing. 

Jon Sparkes, chief executive of Crisis, said: "London is one of the wealthiest cities in the world – the fact it is facing such a rise in homelessness is nothing short of a scandal. By pledging to Lead London Home the next Mayor will be pledging to arrest this rise and to help the thousands of people who find themselves homeless each year."

Rick Henderson, chief executive of Homeless Link, said: "The priority after May must be prevention, including helping those with the most complex needs and providing specialist support for vulnerable and minority groups. For those already homeless it is vital to ensure that there is a clear route off the street, as well as investment in new homes."

Jon Kuhrt, head of social work at the West London Mission, said: "Churches and Christian groups are doing a huge amount to alleviate the homelessness crisis. Here in Westminster, where the numbers of rough sleepers is the highest in the country, the West London Mission coordinates 13 churches and a synagogue in the Westminster Winter shelter which runs between October and May. Our Day Centre for rough sleepers has been operating for over 40 years and sees up to 100 homeless people every day.

"But alongside all this help, we must speak out about the issues which are causing so many to feel the pavement, the park or the night bus is their only housing option. We need to be both practical and political. This is why the Lead London Home campaign is so vital – churches, charities and the general public need to get behind this campaign and send a clear message to the new mayor that housing is the number one issue for Londoners and that speedy action is urgently needed to stem the flow of people sleeping rough on our city's streets."