Plans to impose a residence test on legal aid eligibility will impede the vulnerable and could even cost the government money. They should be voted down.

How do you fix a problem that you don’t know exists? That is the task that David Cameron’s government set itself when it proposed, as part of the Ministry of Justice’s latest attack on access to justice ‘Transforming Legal Aid’, to impose a residence test on anyone who needed legal advice but lacked the means to afford it.

From August, the lord chancellor Chris Grayling says only those with a year’s residence in England and Wales before they ask for advice will be eligible to apply for legal aid.

The test, to be voted on by the House of Commons today, has been condemned by three all-party parliamentary committees, leading judges and independent charities. They point out the proposals may be unlawful and are unsupported by any evidence that they will save money or discourage litigation. The Joint Committee on Human Rights even suggested that they are in defiance of our legal obligation to uphold the UN Convention on the Rights of the Child.

Indeed Grayling’s plan to ‘deny foreigners legal aid’ as he put it in the Daily Mail, may well cost money. More litigants in person clogging the courts, more hardship and distress cases if meritorious cases fail and a bureaucratic burden on small solicitors’ firms and advice agencies. In any other context the government would describe this as red tape.

So who are the undeserving objects of the coalition’s ire?

They may be non-UK residents who nevertheless have a compelling claim, like the Ghurkhas refused the right to settle in the UK or Afghan interpreters whose lives were at risk for the assistance they gave British forces.

They may be UK citizens who have been resident abroad for a time. Although serving members of the armed forces overseas are exempt from the test, if they have recently left the forces, they and their families will not qualify.

Thirdly, and most unjustly, will be UK citizens who are entitled but for one reason or another are unable to provide evidence that they are citizens and have been residents for the preceding 12 months.

Homeless families may find it difficult to prove eligibility. Dementia sufferers, people with learning difficulties or mental health needs, those in care homes like Winterbourne View may all fall foul of stringent evidence criteria.

There is some exemption for trafficking victims, but only for immigration and employment claims and claims against the trafficker, not for example for health needs. Domestic violence victims, asylum seekers, detainees will be eligible to make some claims but not others.

The test now has a long tail of hotchpotch exemptions in an attempt to make it look less crazy: for example children under 12 months old who would originally have been barred from applying for legal aid can now do so.

But the idea should have begun and ended as a soundbite from Chris Grayling, the worst lord chancellor in living memory. It penalises the vulnerable, limits access to justice in an arbitrary way, breaks our international law obligations and, according to the government, there is no evidence that it delivers a penny in savings.

We should, as one lone Lib Dem MP said when we debated the test, be ‘ashamed’ to introduce it. We, and they, should vote it out.

Andy Slaughter MP is shadow justice minister