He was the principal private secretary to trade minister Mike Moore in the 1980s before being appointed New Zealand's high commissioner to Papua New Guinea from 1989 to 1993 and ambassador to Iran from 1993 to 1995.

[8][9] Hayes took an active role alongside the then Minister of Foreign Affairs and Trade, Don McKinnon, during the Bougainville conflict in the 1990s.

In 1997, he returned to Port Moresby to negotiate peace talks between the Papua New Guinea government and the Bougainville Revolutionary Army (the BRA).

[10][11][12] In the 1999 Queen's Birthday Honours, Hayes was appointed an Officer of the New Zealand Order of Merit, for services to the Bougainville peace process.

[13] He retired from the foreign ministry in November 2003 and settled in Greytown, where he maintained an apple orchard and worked as a property developer.

In his maiden statement, given on 17 November 2005, Hayes criticised staff growth in the Ministry of Foreign Affairs and aid given to Niue.