An appeal Court ruling that a Christian woman must work on Sundays against her religious belief has, surprisingly, given Shabbat-observant Jews better legal protection, according to lawyers.

Devout Christian Celestina Mba lost her Court of Appeal case in which she claimed that South London’s Merton Council had discriminated against her by refusing to give her Sundays off.

The care-home worker wanted the right not to work in order to observe the Christian Sabbath.

Appeal judges, upholding an employment tribunal decision, said Mrs Mba lost the case because her contract obligated her to work on Sundays.

But they upheld her claim that a majority of people in a religious group did not have to hold a belief for it still to be protected by the law.

Employment law expert Elaine Aarons, a partner at Withers LLP, said the ruling confirms for the first time a previously untested legal right for Jews to ask employers for Shabbat off, even if the majority of Jews are willing to work on Saturdays.

“Changes in the law in 2003 allowed Jews to rely legally on a religious belief that they must not work on Shabbat, even if the majority of Jews do not observe it,” she said.

Daniel Naftalin, a partner in the employment department of law firm Mishcon de Reya, said Mrs Mba’s case “adds clarity where previously there was uncertainty”.

He said: “It would be a brave employer who relied on this case to take liberties on issues of religious tolerance.”

But, he added, there was a caveat. “If it is not viable to do a job without working on Shabbat, there is an acceptable legal argument that the employer does not have to accept religious needs.

“It makes sense for Jewish employees to put religious needs into their contracts.”