Government plans to introduce a residence test for access to legal aid will breach an international convention on children's human rights, MPs and peers have warned.
The Joint Committee on Human Rights said the policy would "inevitably" contravene the UN Convention on the Rights of the Child (UNCRC) by preventing some children from being effectively represented in proceedings affecting them.
The parliamentarians suggested that all children should be exempt from the residence test, which is aimed at making sure that only those with a "strong connection" to the UK can benefit from civil legal aid.
Under the plans, with certain exemptions, applicants would have to have completed a 12-month period of continual residence in the UK and be lawfully resident at the time legal aid was sought.
Ministers hope that the test will come into force in August, but the MPs and peers called on the Government to withdraw the legislation and think again, raising concerns about breaching the UNCRC's Article 3 which states that the child's best interest should be the "primary consideration" or Article 12 which protects the child's right to be heard in proceedings.
The Committee's report said without access to legal aid children would "rarely be capable of representing themselves in legal proceedings in which their best interests are at stake, as they may be unable to access a litigation friend or a legal representative and will not have the capacity to represent themselves effectively".
The report said: "We cannot see any way in which this proposal can be compatible with the UK's obligations to ensure that the views of children are heard in any judicial or administrative proceedings affecting the child under Article 12 UNCRC, or to ensure that the child's best interests are a primary consideration in such proceedings under Article 3.
"To comply with those obligations, which are owed to all children in the UK regardless of their residence or other status ... legal aid must in principle be available to make the child's rights under Articles 3 and 12 practical and effective for those who have no recourse to other appropriate means.
"As long as children have a legal right to take part in legal proceedings which affect their interests, it is wrong in principle, and unlawful, to make it more difficult for a particular group of children to exercise that right.
"We conclude that the residence test will inevitably lead to breaches by the United Kingdom of the UNCRC, and in particular Articles 3 and 12, in individual cases, because it will in practice prevent children from being effectively represented in legal proceedings which affect them."
The Committee's Labour chairman Hywel Francis said: " We do not feel that the Government has supplied enough evidence to justify why children should not be excluded altogether from the residence test, and we feel that it has not given enough thought to some of the practical obstacles which children will face."
The Ministry of Justice said t here are exceptions to the residence requirement for certain cases relating to an individual's liberty, where the individual is particularly vulnerable or where the case relates to the protection of children.
A spokesman said: "The residence test will focus our limited resources for civil legal aid on those who have a strong connection to the UK, and not those who have barely stepped over the border or are here illegally.
"We want any reform to be the right reform, which is why we have listened very carefully to the Committee's previous recommendations and built in a number of additional safeguards."