[6] In September 2011 Carter resigned from Parliament following his appointment to a United Nations position in Afghanistan where he served for 4 years.

At the 1987 election Carter stood unsuccessfully as the Labour Party candidate in the Albany electorate, losing to National's Don McKinnon.

In a local-body election in 1988 he stood as a candidate for the Te Atatu ward of the Auckland Regional Authority, but was unsuccessful.

[11] In 1994, Carter was named by the Speaker of the House Peter Tapsell for calling John Banks a hypocrite over his anti-abortion stance on abortions.

[14] After losing his seat, Carter started one of the first branches of New Zealand Rainbow Labour for centre-left lesbians, gays, bisexuals, transgender people (LGBT) and others during the 1996–1999 term.

He had been a strong advocate of gay equality for some time, and continued this role on entering Parliament.

In the case of Carter, he was accused of purchasing personal items with the card, which was outside the rules for Ministerial expenditure as a minister under the former Clark government over a six-year period.

Carter's demotion included removal from the front bench, and loss of the shadow portfolio of Foreign Affairs.

[17] On 29 July 2010 Carter was suspended from the Labour Party caucus for allegedly being behind an anonymous letter sent around the press gallery claiming there was a leadership challenge against Phil Goff; a charge he later admitted.

On 18 October 2013, Carter was waiting for a colleague to leave his compound in Kabul when a suicide bomber attacked a passing military convoy on the street some 25 metres (82 ft) away; he was separated from the blast by a glass wall.

[18] In September 2015 Carter was appointed as the Senior UN Advisor for Rakhine State in Myanmar after serving for 4 years in Afghanistan.

In 2019, Carter retired from the United Nations after seven years' service and returned to New Zealand to live in Te Atatū.