Seventy years ago, in 1948, the Empire Windrush docked at Tilbury, England, having sailed into history having begun its journey in Jamaica. The 492 passengers were the earliest group of post-war Caribbean migrants and achieved an almost iconic status.

In recent months, the Empire Windrush has given its name to a scandal that obliged Theresa May to apologise and Amber Rudd to resign. Millions have been appalled at how we could have treated people who had travelled here legally, and were certain that they were British, with such cruelty.

The Windrush generation, which my mother could be regarded as part of, came here after the war to help rebuild this country. They often did the jobs others were unwilling to do.

Yet under this callous government, some of these people have refused medical treatment even when suffering from cancer. Others have been refused benefits to which they were fully entitled – including housing benefit, making people homeless. Others lost their jobs when a new owner of their company insisted on documentation they had never had.

People were locked up in immigration detention centres, and others refused entry back into this country after going to the Caribbean for a holiday. A number were deported.

The reality is that the government’s response has been simply unacceptable at every stage of this scandal. Again and again, it has dragged its feet on coming forward with the full story about what has happened.

The government and Prime Minister must come clean about how this policy came about. It is not as if they weren’t warned. I and others told them in 2014 that this scandal would be the predictable consequence of their policies. They cannot claim ignorance. They were warned – but they pressed ahead anyway.

As we celebrate the contribution of the Windrush generation, we should also use this opportunity to argue for a new approach on immigration policy more generally. One of the most common myths about immigration is that we aren’t allowed to talk about it. Yet since the Empire Windrush docked at Tilbury 70 years ago, parliament has passed: the British Nationality Act 1948; the Commonwealth Immigrants Act 1968; the Immigration Act 1971; the Immigration Act 1988; the the Asylum and Immigration Act 1996; the Immigration and Asylum Act 1999; the Nationality, Immigration and Asylum Act 2002; Asylum and Immigration Act 2004; Immigration, Asylum and Nationality Act 2006; UK Borders Act 2007; Borders Citizens and Immigration Act 2009; the Immigration Act 2014 and the Immigration act 2016. This is not the legislative record of a political class that doesn’t want to talk about immigration.

In truth, the scandal surrounding the Windrush generation relates to how we have been talking about immigration. It is linked to how too many politicians, newspapers and commentators have been using negative language and promoting antipathetic views.

A number of those same people now pay tribute to the contribution of the Windrush generation. They are right to do so – some might even say it’s long overdue – but there is nothing uniquely saintly about that generation. They reflect what migrants do generally: move for better opportunities, for themselves and for their families. They work hard, they contribute. They enrich our culture, society and diversity.

The consistently negative narrative about migrants meant it became gradually easier to treat them in a way that, when held up to the public gaze amid the Windrush scandal, seemed harsh and inhumane.

Migrants have always been demonised by racists and xenophobes, but they have also been increasingly demonised by those seeking political advantage. And guess what? That has increased the number of genuine and avowed racists. The answer of some politicians was to pander to that racism even further, so the vicious circle takes another turn.

It is time to break that vicious circle. I want there to be a new cycle. One where we call out the demonisation of migrants, and we try to correct terrible policies that have been implemented.

The Windrush generation are really the first, and among the most heart-rending, victims of the Conservative Party’s ‘hostile environment’ policy. They did not need papers to claim their rights to NHS treatment or benefits until that policy was introduced under Theresa May.

The ‘hostile environment’ has infected almost every area of life, from schools and universities to employers, state agencies and landlords. All have been turned into internal border guards.

It was politically-motivated and driven, not a product of analysis of our economic or social needs. It is a failed policy that must come to an end, as should the Tory cover-up over the Windrush scandal.

Diane Abbott is shadow home secretary and MP for Hackney North and Stoke Newington.

@HackneyAbbott