Strengthening the powers of the English children's commissioner will be at the heart of lobbying to change parts of the Children Bill.
The Liberal Democrats are to table an amendment in the House of Lords in the coming weeks following fears about the commissioner's independence from government.
Liberal Democrat peer Baroness Walmsley's amendment would give the commissioner the power to investigate complaints without the agreement of the education secretary, as well as bring and intervene in legal proceedings.
The commissioner will have to follow the UN Convention on the Rights of the Child. Walmsley said the proposals in the Bill were "out of step with the rest of the UK and international standards".
