Obituary: Dame Barbara Mills, director of public prosecutions in England

Dame Barbara Mills became one of the most powerful law officers in England and in the 1990s was appointed director of public prosecutions (DPP), a post she held for six years amid growing controversy. She did much to reform the institution but her critics considered Mills had made the DPP too bureaucratic and confrontational.

She was the first woman to head the Crown Prosecution Service (CPS) which removed the responsibility of prosecuting criminals from the police. Some legal observers viewed the new procedures with some alarm.

Furthermore, when she took over the job in 1992 it was the centre of controversy as her predecessor, Sir Allan Green, had resigned after being caught kerb-crawling in King's Cross.

As a QC, Mills had had an outstanding career, prosecuting Michael Fagan, who had broken into the Queen's bedroom at Buckingham Palace, and defending Winston Silcott, accused - and initially convicted - of murdering PC Keith Blakelock on the Broadwater Farm estate in north London. But Mills displayed an eye for detail and command of a complicated brief when she was number two in the prosecution team for the Guinness case. That was the biggest criminal trial of the era and attracted widespread publicity. It gained a certain notoriety especially in Scotland simply because of the dramatic takeover and outsized personalities involved.

The bid was particularly controversial in Edinburgh where Distillers was one of the leading public companies and had a proud history of whisky and gin distilling. Its shares were widely held by the Scottish financial institutions and its head office in Torphicen Street in Edinburgh's Haymarket ensured it had a very definite Scottish identity. Guinness was viewed as an outsider and many in Scotland preferred a rival bid from Sir Jimmy Gulliver's Argyll Group.

Essentially, the Guinness Four - Ernest Saunders, Gerald Ronson, Jack Lyons and Anthony Parnes - were tried in 1990 after the successful takeover of Distillers by Guinness. The four stood trial for attempting to manipulate the share price of Distillers in the 2.7 billion takeover. They bought shares in Guinness to ensure their bid was more advantageous to shareholders than the offer from Argyll Group.

Mills unravelled the financial complexities with a cool and professional manner. Her meticulous attention to the minutiae of the various transactions was much remarked upon and after 112 days all four were convicted, although there were successful subsequent appeals.Huge sums were involved: Saunders admitted he had raised $100 million through the Wall Street broker Ivan Boesky but there is little doubt that had Mills not been able to present the facts in a straightforward and comprehensible manner the trial might well have collapsed.

Barbara Jean Lyon Warnock was the daughter of a chartered accountant and after St Helen's School, Northwood she won a scholarship in 1961 to read Law at Lady Margaret Hall, Oxford. She was called to the Bar at the Middle Temple in 1963, becoming junior Treasury counsel in 1981 and taking Silk in 1986.

After the Guinness trial Mills was appointed to the Serious Fraud Office (SFO) where she presided over several high profile cases, including the Bank of Credit and Commerce International and Polly Peck. The latter involved 70 charges of false accounting alone. After some other prosecutions - notably the second Guinness trial of 1992 and the collapse of the Blue Arrow rights issue - there was criticism of Mills: the SFO was dubbed the "seriously flawed office".

As DPP Mills assumed total responsibility for the CPS, and became personally involved in many of the important cases it handled although there was some dissatisfaction from the police over the the department's failure to prosecute in many cases, especially that of the five men arrested for the murder of Stephen Lawrence in 1983.

Mills was widely respected and an undoubted role model for young women in the profession. She carefully balanced the demands of her job with family life - which were increased when, in 1995, her husband was stabbed outside their house in north London.

Throughout her career Mills attracted much publicity and the many profiles of her seldom failed to mention her perfect long fingernails, matching lipstick and earrings. She was a friend of many of the leading politicians in New Labour - particularly Tony Blair.

Mills was created a Dame in 1997 and served as a part-time adjudicator for HM Revenue and Customs when she retired. She married John Mills in 1962. He, their three daughters and a son survive her.