The new “homelessness minister” has begun her job badly. Heather Wheeler claims not to know why homelessness has risen for seven consecutive years – that’s every year since she was elected. She has also been gazumped by the Cabinet Office minister, David Lidington, who is also chair of the government’s rough sleeping advisory panel. The panel has finally held its first, belated, meeting.

Wheeler needs to get to grips with the brief she has held since January. The first step in tackling any problem is understanding what has caused it. Admitting she doesn’t understand this basic element of her brief is terrible news for homeless people and bodes badly for her government’s commitment to halve homelessness by 2022. I welcome this target as co-chair of the all-party parliamentary group for ending homelessness and support the minister’s claim she will “move heaven and earth” to tackle the problem, but the first step is a hard, objective look at how it has come about.

The government’s absence of leadership created a vacuum that charities and others have struggled to fill

Since austerity programmes pursued by the government in 2010, councils’ ability to tackle homelessness has been undermined by a dramatic reduction in funds to help build sufficient, genuinely affordable homes. Public health cuts and attacks on community pharmacy budgets have ended some drug and alcohol cessation services. Mental health services have been axed and direct financial support has been pulled from people’s pockets.

The government recently announced, for example, it would have to reassess 220,000 people with mental health problems for personal independence payments after failing to properly take into account the impact of their conditions. The Department for Work and Pensions fought the case through the courts, wasting thousands of pounds of taxpayers’ money, but has finally had to admit its mistake. Given that 40% of homeless people have a mental health condition, the scale of the government’s damage to this group is incalculable.

With falling financial support, a failure to tackle the housing crisis, and a reduction in support to manage mental health conditions, the scene has been set. Universal credit has made matters worse for those people who struggle to manage finances, especially for the month-and-a-half automatic waiting period for a first payment. The personal debts and arrears clocked up in this period are worth about £5m to my local council alone and universal credit was specifically cited as the cause of homelessness by one man I met recently while out with St Mungo’s in Southwark.

The minister’s failure to understand the root of the problem hasn’t prevented its rising visibility. With more than 300,000 families now in temporary accommodation and almost 5,000 people rough sleeping nightly, people are more aware of the issue. The death of a man on parliament’s doorstep shamed the UK and led to greater demands for action. Wheeler needs to catch up.

The government’s absence of leadership created a vacuum that charities and others have struggled to fill. The mayor of London, Sadiq Khan, and Manchester’s mayor, Andy Burnham, are pioneering their own efforts and extending help. The Robes Project in south London now covers 28 churches in two boroughs for the whole of winter, offering a safe, warm space for homeless people, and in some shelters even a hot meal. The appetite for change is growing: witness the thousands of referrals from the general public to the Streetlink app in London to help rough sleepers into shelters.

The minister’s claim not to know why the problem has become so dramatic is a revelation. In any other job, I suspect an employer would be seeking her resignation. But then, Wheeler reports to a government with collective responsibility for causing this growth in homelessness. Ignorance may seem preferable to culpability.

• Neil Coyle is Labour MP for Bermondsey and Old Southwark