The Board of Deputies and strictly Orthodox charity Interlink have joined a coalition of Christian groups in opposing welfare cuts, which they say will hit large families.
A briefing paper prepared for the House of the Lords, which is due to discuss the proposal next week, describes the measures as "fundamentally anti-family".
Their concern has been triggered by plans in the Welfare Reform and Work Bill to limit low-income families to claiming tax credits for no more than two children.
A Board spokesman said that "this will adversely affect thousands of Jewish children in working households, with the pain being felt particularly in the Charedi community".
The paper points out that the proposed cut "will disproportionately affect families where perhaps because of the parents' faith, there is a devout desire to avoid contraception or