In the aftermath of the Windrush scandal, government ministers have repeated the same refrain: the detention and deportation of ethnic minority British citizens was a result of a bureaucratic mistake and administrative error.

I do not buy this argument. This is the same Home Office that mistakenly deported at least 1,000 highly skilled migrants. It is the same Home Office that wrongly accused thousands of students of cheating on an English language test and deprived them of their status, and the same Home Office that misses deadlines, loses my constituents’ passports and takes years to respond to basic leave to remain applications.

If Windrush and subsequent scandals have taught us anything, it is that there is a deep-rooted and systemic problem with our immigration system. I proposed a set of reforms in Open and Ethical, a new Fabian Society report, which would transform our immigration system, making it fair, humane and respectful of human dignity.

Among the most dehumanised groups in Britain are undocumented migrants. They are considered “illegals” or “aliens” before they are human beings – a hidden population that we know very little about. In the national consciousness, we imagine undocumented people waiting in their thousands to steal British jobs, abuse our welfare state and overcrowd our hospitals. The tabloids tell tales of illegal immigrants swindling thousands of pounds in benefits; the US president demands that we deport them, and puts their children in cages.

The government has responded to this concern by introducing policies that exclude undocumented migrants from working, renting or accessing public services. The effect of these policies is to create a hostile environment that makes life so unlivable for those illegally resident in the UK that they are forced to leave.

The resulting legislation, carried out over two immigration acts, was responsible for a shocking disregard for the rights of migrants and ethnic minority British citizens, and ultimately proved ineffective at reducing illegal immigration.

It is time to rethink our attitudes to undocumented migrants in this country. No matter how punitive and aggressive its policies, the government will never be able to deport all undocumented migrants, or close our borders entirely.

The invisible nature of undocumented migrants makes it impossible to gauge how many live in Britain. If you read the tabloid press, you would be forgiven for thinking that there are millions of people living without status, but the numbers are probably closer to 600,000. Roughly 100,000 of them are children – some of whom have been born into invisibility, and have had to grow up in hiding.

We are talking about single parent families, young children and adolescents old enough to go to university. We are talking about low earners, struggling to get by and pay their bills. They are carers, builders and domestic workers. Many have arrived in the UK from countries that have born the brunt of British colonial rule, with dreams that their children and grandchildren might be able to have better lives.

The Home Office’s ineffective war against undocumented immigration has built a “shadow economy” where workplace exploitation, human trafficking and other criminal behavior is rife. The question hinges on whether the government should maintain the illegal status of these undocumented migrants, or regularise their status, enabling them to pay income tax and national insurance, and to live safely and integrate into society. I support the latter option.

According to the Institute of Public Policy Research, undocumented workers in the UK would pay between £1bn and £3bn a year in tax. In 2005, the socialist government in Spain introduced an amnesty which regularised the status of roughly 700,000 migrants. As a result of the three-month amnesty, the Spanish government reported that it netted 750 million euros in extra taxes and national insurance provisions. It also credits the policy with reducing economic exploitation of vulnerable people throughout the country.

The arguments for a one-off immigration amnesty do not only come from the left. Politicians of all stripes have made this case, including former Foreign Secretary Boris Johnson. In 1986, Ronald Reagan allowed roughly 3 million undocumented migrants to gain legal status in America.

The reforms I have suggested would mark a much-needed sea change in immigration policy. Following Windrush, there is public appetite to reject the cruel and inhumane policies of the past and build an environment for migrants that is both fair and practical. It’s time politicians listened to the lessons that Windrush has to offer.