LONDON (Bloomberg) — Britain’s tax and spending watchdog attacked the revenue office for failing to prevent tax avoidance among individuals and said more needs to be done to tackle the aggressive use of loopholes.The National Audit Office praised Her Majesty’s Revenue & Customs for raising as much as £200 million ($318 million) from rich tax avoiders in the fiscal year ended March while urging it to claw back money from the 41,000 open cases on its books.“HMRC must push harder to find an effective way to tackle the promoters and users of the most aggressive tax-avoidance schemes,” Amyas Morse, head of the NAO, said in a statement in London yesterday.The revenue department requires accountants to disclose some types of tax avoidance that is legal and used to minimise tax liabilities. Morse said HMRC must do more to limit so-called partnership-loss schemes used by 30,000 people.