In 1608 he was appointed Master in Chancery in Ordinary and in 1611 was appointed to the council of Queen Anne, wife of James I. He was growing in wealth and status and is reported to have offered £30,000 to become Lord Chancellor, without success. Bennet, who was interested in the affairs of Oxford University, was asked by Sir Thomas Bodley to act as fund-raiser for the Bodleian Library, a task he carried out efficiently. Bennet was one of the first governors of Pembroke College, Oxford. He was elected MP for Oxford University in 1614 and 1621. However, he was accused by Richard Kilvert in Parliament of extracting bribes and excessive fees in his judicial work. The issue was debated in his absence, Bennet pleading ill-health, and it was decided that he should be expelled from the House of Commons and the case referred to the House of Lords. He was placed under house arrest. When he appeared before the House of Lords, he said that he could account for all but £4,000 of the money that had passed through his hands. He was bailed in the sum of £20,000 and ordered to pay to Oxford University £1,000 that he still had as executor of Thomas Bodley's estate: he only paid £550. When the case was eventually tried, Bennet's counsel put up a weak defence. Bennet was fined £20,000, but punishments of imprisonment and disqualification from office were later lifted. It was said that his profiteering from his post overshadowed that of Francis Bacon: "Sir John Bennet hath made my Lord Chancellor an honest man". Bennet married firstly Alice Weekes daughter of Christopher Weekes of Salisbury and had four sons and two daughters. She died in 1601 and he married secondly Elizabeth Lowe, daughter of Sir Thomas Lowe, alderman of London. She died in 1614 and he married thirdly Leonora daughter of Adrian Vierandeels of Antwerp, a widow. Bennet died on 15 February 1627 and was buried at Christ Church, London.