am i entitled to working family tax credit

Tax Credits replaced tax allowances and most accountants have left claiming them to their clients not considering them to be part of their remit. They have preferred to give taxation advice such as whether to incorporate and other tax saving strategies. The amount of tax payable affects the net monies available for the family to spend. So do "Tax Credits"! "Tax" is in the title. So how can we increase the family budget by making sure the Tax Credits claimed are the maximum available? If you are an accountant could this neglect lead to a claim against you for professional negligence?