Tew's career in sports administration began in 1982 as secretary-general of the New Zealand Universities Sports Union. He served in that role until 1987, when he became the general manager of the Hillary Commission. From 1996 to 2001, he was chief executive of the Canterbury Rugby Union and the Crusaders.[1][4]
Tew joined Rugby New Zealand as general manager in 2001, and became deputy chief executive in 2003.[4] He took over as chief executive from Chris Moller after the poor showing of the All Blacks in the 2007 Rugby World Cup. Under Tew's tenure, Rugby New Zealand suffered its worst financial result ever in 2009/2010, losing $15.9 million in 2009 due to the global economic recession and investments due to hosting the 2011 Rugby World Cup, before taking steps to improve its revenues, including signing a five-year broadcast deal and securing a sponsorship with Adidas through to 2019.[5]
Tew stepped down from his position as CEO of New Zealand Rugby at the end of 2019.[6] In 2020, he was contracted by Sport New Zealand to conduct a review of the impact of the COVID-19 pandemic on professional sports in New Zealand.[7]