Lady Hale says the government's proposed cuts will have a 'disproportionate' effect on the most vulnerable in society

The only female justice on the supreme court, Lady Hale, has highlighted the impact of the proposed cuts in legal aid, declaring that they would have a "disproportionate effect upon the poorest and most vulnerable in society".

Her comments came as solicitors warned that more than a third of law centres in England and Wales providing advice to the disadvantaged would be forced to close under the legal aid plans.

On Wednesday the government will push the second reading of its legal aid and sentencing bill through the Commons only a week after the repeatedly delayed legislation was first introduced into parliament.

In his speech last week, the justice secretary, Kenneth Clarke, signalled that help might be given to law centres because so much of their funding would be withdrawn.

Figures provided by Julie Bishop, director of the Law Centres Federation, show that of 52 centres in England and Wales at least 18 will have no alternative but to shut down because three-quarters of their income comes from legal aid that will no longer be available.

Law centres help those who cannot afford to pay a solicitor to obtain legal advice and support in housing, welfare, medical negligence and many other areas that will soon no longer be eligible for legal aid.

Last year, law centres helped 120,000 people, Bishop said. Soon, because of the government's determination to slice £350m out of its annual £2.1bn legal aid budget, the number who can be helped will fall by two-thirds to 40,000.

In an unusually forthright speech that appeared to address those concerns directly, Hale, who is patron of Hammersmith and Fulham law centre, voiced worries circulating in the broader legal community about problems of access to justice for the less well-off.

"There is a well-known ironic saying," she said in a speech to the Law Society on Monday evening, that "in England, justice is open to all – like the Ritz."

Legal aid was now being removed from "most civil and legal cases", she noted. But providing legal advice at an early stage, she said, could often save greater costs for government agencies at a later stage when problems spiralled out of control.

"These plans will, of course, have a disproportionate effect upon the poorest and most vulnerable in society."

The government's own impact assessment had acknowledged the problem, Hale said, adding that the Legal Action Group "fears 'that this would lead to an underclass of people disenfranchised from civil justice and indifferent to the rule of law'".

British courts, she said, have had to defend right of access to the courts in the face of government insistence that the civil justice system should pay for itself.

Her speech, which she entitled Equal Access to Justice in the Big Society, is – not least because of its timing – likely to be received as a direct challenge to one of the government's major cost-cutting measures.

"Courts are, and should be, a last resort, but they should be a last resort which is accessible to all, rich and poor alike. The big society will be the loser if everyone does not believe that the law is there for them," Hale said.

Proposals in the government's bill to introduce means-testing in police stations for those arrested to ascertain whether they are entitled to legal advice also came in for fierce criticism from the Law Society, the body that represents solicitors.

Des Hudson, the Law Society's chief executive, said: "We will go back to the excesses of the 1970s, and run the risk of people being verballed [have false incriminating statements recorded] by police officers if there are no solicitors available to advise those who have been arrested."

The Law Society claimed the government's definition for providing legal aid for victims of domestic violence was still at odds with the definition currently used by the courts.

Linda Lee, the society's president, said: "The fact that under the government's current proposals many such victims of serious injury will now lose up to 25% of their compensation, or won't be able to afford to take a case in the first place, will be found abhorrent by many."

The Bar Council, which represents barristers, has written to MPs expressing "serious concerns" about the bill. It accused the government of ignoring "thousands of responses to its consultation, which warn of the serious consequences of its proposals".

The Bar Council said: "If legal aid is withdrawn from substantial areas of law, many people will be unable in practice to enforce their legal rights. Without the benefit of quality legal representation, vulnerable people and honest, hard-working families will have to go to court by themselves … The proposals to withdraw entire areas of legal aid from scope will create acute problems about access to justice."

Peter Lodder QC, chairman of the Bar Council, said: "The bill's proposals will cause great harm to ordinary people. We continue to make the case for access to justice in the strongest terms. There has been much public debate about sentencing. There must be a similar scrutiny of these wide-ranging proposed changes to legal aid.

"A cut-price, DIY justice system, which will actually end up costing more money, rather than saving it, is in no one's interests."

The Commons health select committee also flagged up concerns about government reforms of 'no win, no fee' contingency agreements. It warned: "This could impact negatively on some of the most seriously injured or disabled claimants, both by reducing the value of final settlements (after erosion by fees) and by undermining access to justice."