Even before the Windrush scandal, it was clear Britain’s immigration system was in desperate need of reform. Like many MPs, I’ve had regular battles with the Home Office on behalf of constituents – from asylum-seekers wrongly refused to visitor visas rejected without reason. You soon learn the grim realities. And the astonishingly costly inefficiency.

But our collective hand-wringing over individual cases won’t do any more. We must face up to the long-term failures of Britain’s approach to immigration and make the argument for an effective, compassionate and liberal alternative.

For too long, politicians with progressive instincts have run away from this debate, too fearful to stick their heads over the parapet. Into the resulting vacuum stepped Nigel Farage et al, enjoying a free hand to exploit public frustration and stoke anti-immigrant sentiment.

That stops now. The Liberal Democrats are demanding better, with radical plans which will be debated and decided at our conference this month to overhaul the immigration system.

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Our new approach would respect the dignity and humanity of all migrants, refugees and asylum-seekers. It would combine efficient processing of applications with effective enforcement of immigration rules.

It would take policymaking out of the discredited Home Office, scrap the targets, bring an end to the “hostile environment” and reduce detention to an absolute last resort. And it would celebrate the many benefits of immigration to our communities, our economy and our public services.

We would, for example, allow asylum-seekers and refugees to work within three months of entering the country. This would enable people to use and develop their skills while waiting for a decision, giving them a sense of dignity and a feeling of belonging to their community. And it makes sense for taxpayers, enabling refugees to contribute to the Exchequer and ensuring that the public doesn’t have to pay the cost of supporting them.

We would ditch the Conservatives’ damaging net migration target. We want to encourage foreign students to come to our universities – to study, research and teach. We want the NHS to be able to recruit the doctors and nurses it needs. And we want British businesses to be free to hire the best workers from anywhere in the world.

To make this happen, we would start by putting the business and education departments in charge of rules governing work permits and student visas, instead of the Home Office. We’d reform the administration of applications – establishing a new non-political organisation with a caseworker model of support and a focus on getting decisions right, first time.

If we are to persuade people of the benefits of legal immigration, we must also show that we have more effective ideas for tackling illegal immigration – whether it’s people overstaying their visas or organised criminal gangs and their human trafficked victims. We won’t create a liberal utopia if we allow criminals to enter and leave the country as they please and prey on vulnerable people.

‘Families belong together’ protests over Trump immigration policy Show all 8 1 /8 ‘Families belong together’ protests over Trump immigration policy ‘Families belong together’ protests over Trump immigration policy Mishawaka, Indiana AP ‘Families belong together’ protests over Trump immigration policy Washington DC AFP/Getty Images ‘Families belong together’ protests over Trump immigration policy New York Mayor Bill De Blasio speaks in Tornillo, Texas alongside the many other US mayors who have called for detained immigrant children to be reunited with their families AP ‘Families belong together’ protests over Trump immigration policy Albuquerque Mayor Tim Kelle leaves a teddy bear as a gift for detained immigrant children in Tornillo, Texas AP ‘Families belong together’ protests over Trump immigration policy Seattle Mayor Jenny Durkan and Los Angeles Mayor Eric Garcetti leave sandals as gifts for detained immigrant children in Tornillo, Texas AP ‘Families belong together’ protests over Trump immigration policy San Diego, California EPA ‘Families belong together’ protests over Trump immigration policy US embassy, Mexico City AFP/Getty Images ‘Families belong together’ protests over Trump immigration policy San Diego, California EPA

Frankly, Conservative policy on illegal immigration is failing: Theresa May’s “hostile environment” isn’t working. Its fishing-net approach catches too many innocent people, wastes huge amounts of money and causes untold misery. The Liberal Democrats would scrap it and replace it with a targeted, intelligence-led approach.

By investing properly in Border Force and the Immigration Enforcement department, and exploiting data from the “exit checks” brought back at our borders by the Liberal Democrats in coalition, we can identify over-stayers more quickly, combat trafficking more effectively, and restore confidence in the wider immigration system.

Our new policy of detention as an absolute last resort won’t just be more humane; it will be more effective and less expensive. Detention centres are always costly and often cruel – Yarl’s Wood alone has spawned countless horror stories.

So we’d reduce the need for detention in the first place with new community schemes used elsewhere and recommended by independent reviews. We’d then limit immigration detention to a maximum of 28 days (as advocated by Detention Forum and other NGOs) – though most people would only be held for one or two nights, and only if they refused to cooperate with the system. Together, this new approach could save around £100m a year, which we would reinvest in priorities like securing our borders.

Having spent 20 years helping my constituents navigate the Home Office’s nightmarish processes, and five years in government arguing against the Conservatives’ net migration target and “hostile environment” policies, I am determined to build a humane immigration system that actually works. These new Liberal Democrat proposals would do just that.