Русско-англо-русский юридический словарь

Several newspapers have criticized the president for inaction. (Longman English Dictionary)

By this stage even Asquith was worried about government inactivity. (Longman English Dictionary)

An omission is a failure to act, which generally attracts different legal consequences from positive conduct. In the criminal law, an omission will constitute an actus reus and give rise to liability only when the law imposes a duty to act and the defendant is in breach of that duty. In tort law, similarly, liability will be imposed for an omission only exceptionally, when it can be established that the defendant was under a duty to act. (Wikipedia)