How do we put a stop to the Channel crossings? There is no doubt that our relationship with France is pivotal. I’m not naive about this: I know a thing or two about negotiating with the French.

Clearly, both the shadow of Brexit and the looming French presidential election are souring the context. But we have found common cause before: securing the Channel tunnel entrance and closing down the Sangatte refugee camp. We must rediscover that spirit of cooperation to ensure that robust patrol and surveillance measures are in place. That is surely not beyond us.

Longer term, the nationality and borders billwill be integral to fighting this perilous phenomenon. The home secretary is undoubtedly committed to finding a solution and she is right on many of the proposed answers: we must take a tough stance on vile people smugglers who trade on people’s lives. But on one specific front, I very much fear she has got it wrong.

The bill contains a proposal to grant the UK unprecedented powers to send migrants to a third country to have their asylum claims processed. This means the government could deport migrants before their applications have been considered, creating an immigration process in reverse: deport first, ask questions later.

Advocates of the “offshoring” policy have used the Australian model, on which it is based, to argue that it was effective in reducing the number of boat crossings. But our geography is entirely different. And the Home Office has not explained where this offshore processing will take place.

The Norwegians have said no. The Albanians have said no. The Rwandans have said no. So now the Home Office is left considering Ascension Island: 2,000 miles from Britain, with no infrastructure on the island and just one weekly flight from Johannesburg, via Namibia. Offshoring started off costing the Australians more than £300,000 a person a year to process but ended up costing more than £2m a person a year. The UK only has even more expensive options.

We now know that in centres on Nauru and Papua New Guinea, many detainees were mistreated, while others languished in limbo year after year with little hope of resolution. We know that the staggering costs were unsustainable and the policy was abandoned. So why are we trying to emulate this failed strategy?

The blanket nature of pre-emptive deportation is particularly worrying. For a deterrent to be effective, there can be no exemptions or exceptions. Indeed, the minister rejected an amendment at committee stage and explicitly ruled out any exemptions. So a pregnant woman, an orphaned child, a young family – all will be deported to a transit country and detained while their fate is decided.

And herein lies a great irony. At least three-quarters of those asylum seekers detained in offshore processing centres by Australia were eventually judged to be genuine refugees. Similarly in the UK, the vast majority of those who claim asylum are granted asylum. Pushing the problem to another part of the world is just a costly way of delaying the inevitable.

From mountains of paperwork and chartering RAF flights, to building the required infrastructure and dealing with foreign bureaucracies, the logistics involve colossal costs the British taxpayer could well do without. At worst, we could inadvertently create a British Guantanamo Bay.

Parliament shouldn’t grant the government a power that it hasn’t explained how it would use. Nor should we grant a power we don’t want to see used. We said no to pre-trial detention. We said no to ID cards. And we should say no to offshoring until the government can explain how and where they plan to do it.

There is no magic solution, but the current proposal will do little to tackle the push factors driving people out of their home countries or the pull factors that attract them to the UK, such as speaking English or a desire to be reunited with their families. Crucially, it will not deter refugees from attempting to reach the UK; they will always look for other ways.

Instead of a policy built solely on keeping people out, the government should consider creating a legitimate route in for genuine refugees. Many will be surprised to learn that the UK does not have a proper scheme in place that allows people to exercise their right to seek asylum. Migrants fleeing repression in Iran or famine in war-torn Yemen are not able to apply at British embassies. They are not allowed to board flights without guaranteed permission to enter the UK. The only options available to them are either illegal or dangerous or both.

Creating new legal and safe routes would be a constructive rather than destructive deterrent. It would give people a chance to make their case and to think again about crossing the Channel. It would send the message that Britain is firm and fair, realistic and compassionate. Only then will we truly take back control.