The government's proposals for dealing with illegal migration have provoked extensive debate but, as ever, that debate has not been improved by slogans and soundbites on either side of the argument.

This is an important area of policy, of great concern to many, so I make no apologies for setting out my position in detail as the Illegal Migration Bill reaches the House of Commons for its second reading.

The starting point should be immigration and asylum policy more broadly.

For anyone with this country's best interests at heart, taking back control of our borders as a result of leaving the European Union must mean being able to determine for ourselves who we should and should not allow to live here, either as migrants who can contribute to our collective economic or cultural prosperity, or as refugees to whom we owe a duty of care as responsible global citizens.

Due to our geographical location, accepting only those who come from adjacent countries which meet humanitarian need criteria is unlikely to meet that duty.

The numbers in the first category should be determined by what our economy and society need and wants, and in the second category by how many people in need our public services and housing stock can sensibly sustain.

Limiting the numbers in either category is a perfectly sensible thing to do and any government must be entitled to take action to ensure that those who are economic migrants should not be able to use the refugee route to enter the United Kingdom if they are not really refugees.

Sir Jeremy: 'The government must act in the face of unprecedented flows of migrants across the English Channel' (image supplied)

Any government is also entitled to reconsider its international law commitments if they are preventing it meeting such clear and legitimate domestic policy imperatives. That includes the European Convention on Human Rights (ECHR).

Of course, writing the rules which will deliver those outcomes is not straightforward and will often be controversial.

I recognise that the government must act in the face of unprecedented flows of migrants across the English Channel in wholly unacceptable circumstances.

I recognise too that deterring people who are not really refugees from making those dangerous journeys and enriching criminal gangs in the process is likely to require a clear, consistent, and robust approach from the UK Government and parliament, and that the Illegal Migration Bill represents a good faith attempt to take such an approach.

However, having considered it carefully, I am concerned that the bill as it is currently drafted will not work, either legally or practically, in delivering the government's objectives.

Legal challenges to the approach the government seeks to take are inevitable and recognised as such by the government.

The fact that legislation is likely to face legal challenge does not make it wrong, but where such challenge is not only foreseeable but foreseen, it obviously makes sense to construct legislation that minimises the scope for successful challenge, as well as to take practical steps outside the legislative language that will also strengthen the argument for it.

On the legislation itself, there are a number of vulnerabilities. The relevance of the ECHR to the provisions of this bill is inconsistently described.

The bill seeks to exclude from operating on its provisions section three of the Human Rights Act 1998 (HRA), which requires all UK legislation to be interpreted, where possible, compatibly with ECHR rights.

Migrants rescued by border force boat as they cross the Channel(image via SWNS)

First, the need for this exclusion is not evident, as section three of the HRA is already explicit that this can only be done 'as far as it is possible to do so', meaning that parliament's clear subsequent wishes to contravene respect for ECHR rights must prevail, even if section three of the HRA is not excluded from operating on that subsequent legislation.

Secondly, excluding the operation of ECHR rights is inconsistent with later clauses of the Illegal Migration Bill, which say that the UK's obligations under international agreements, specifically including the ECHR, may be used to persuade it not to apply the long-term sanctions for which the bill provides on those defined as relevant illegal migrants.

I will not go into detail on the likely legal challenges to the reduction of protections under the modern slavery regime for those who qualify as illegal migrants under the bill, or the intended exclusion of judicial review of ministerial decision making on the treatment and detention of such migrants, but the defensibility of these proposals, in a court of law and in the court of public opinion, is likely to depend on how the Bill balances fairness to the individuals affected with fairness to society as a whole.

That balance will in part be tested by reference to the likely treatment of children.

The bill requires the refusal of later applications for entry clearance by a migrant who has sought to enter the UK illegally within the terms of the bill.

The prohibition on entering the UK subsequently is intended to be lifelong and the triggering illegal entry could take place at any age.

As I read the bill therefore, a migrant brought into the UK illegally by their parents as a baby (and therefore without any choice in the matter) would be prevented from entering the UK lawfully as an adult decades later.

Such consequences could only be avoided if their imposition would constitute a breach of the UK's international law obligations (including, as mentioned earlier, under the ECHR) or, in the case of shorter-term permissions to enter the UK, where there are 'compelling circumstances' in relation to the individual which would make it appropriate to grant the subsequent application.

Interestingly, discretion based on 'compelling circumstances' is not available in relation to longer-term entry arrangements, including indefinite leave to remain or citizenship.

Far-right protestors clashed with police during a demonstration outside a hotel housing asylum seekers in Yorkshire (image via SWNS)

This would mean that, in the case of someone subject to this bill as a result of illegal entry as a baby, as an adult they would be unable to gain long-term leave to remain in the UK as the spouse of a UK citizen, for example.

I am not convinced the bill strikes the right balance in this respect.

That brings me to my practical concerns. As the government approaches inevitable legal and political challenges to the provisions of this bill, it should ensure that it has the most persuasive case for the necessity of the measures it proposes, and it should be ready to deliver the real-world effects the policy demands and the legislation would authorise.

I have concerns on both counts. The case for tough action against those who seek to enter the UK illegally and unsafely is stronger if it is clear that there are safe and legal routes which those in genuine need could use instead.

That is not currently clear, beyond schemes specific to countries like Ukraine, Afghanistan, and Hong Kong.

Those crossing the Channel in small boats are sometimes accused of 'jumping the queue' for entry into the UK.

Being punished for jumping the queue is legitimate if there is a queue and it is clear how you might join the end of it, less so if the queue is hard to find.

The government can and should do more to clarify the schemes which are available for those genuinely seeking asylum and expand them, if necessary, subject to the point on numbers I made earlier.

The case for tough action along the lines of the bill would be stronger following such clarification. The case for the bill would also be stronger with clarity on where illegal migrants would be detained, as the bill requires them to be for at least 28 days in almost all cases.

Again, I do not yet detect that clarity.

I repeat that I do not believe the government's approach in this bill is wrong in principle, but it can only be justified with a clear demonstration that those deserving admittance to the UK could get it another way; with clear evidence that the practical measures needed to implement the provisions of the bill are in place; with great care taken to avoid unfair and disproportionate outcomes in individual cases; and with proper recognition that judicial scrutiny is part of ministerial accountability.

I am not currently persuaded that these requirements are met in the Illegal Migration Bill as currently drafted and therefore I could not support it at this stage.