Britain's leading Jewish school has told the Supreme Court that it had discriminated against a boy of 12 on religious rather than racial grounds when it denied him a place.

A crowded court heard Lord Pannick QC, claim that the boy was refused because the chief rabbi deemed his mother's conversion to Judaism invalid.

JFS had double the number of applicants to places, so children whose mothers were recognised as Jewish were given priority. The boy, known as M, was refused entry because he did not fall into this category, said Lord Pannick, who is representing JFS.

The boy’s father is Jewish by birth, keeps kosher, prays regularly and attends synagogue. But one of the nine judges said: "M would be regarded as Jewish by almost everybody as Jewish. The people who don't regard him as Jewish are the Orthodox community."

The school, in Brent, north-west London, went to the supreme court after three judges at the Court of Appeal ruled in June that its entry criteria racially discriminated against the boy.

Lord Pannick said M would be regarded as Jewish by a Jewish school which applied criteria under Reform, Masorti or Liberal Judaism movements.

“The difference in the result is not on the ground of M’s ethnic origins. It is on the ground of a religious dispute between Rabbis about who is a Jew.

“Our case is that the refusal of the place to M was not an act of race discrimination - that is, less favourable treatment on the grounds of ethnic origin.

“We say M failed to secure a place at the school because and only because of the religious criteria applied by the Chief Rabbi as to who is Jewish.”

The appeal judges had misinterpreted the law in finding that the school’s admission criteria discriminated on racial grounds, he said.

The case is due to run for three days.