The Munsinger Affair was Canada's first national political sex scandal. It focused on Gerda Munsinger, an East German prostitute and Soviet spy living in Ottawa who had slept with a number of cabinet ministers in John Diefenbaker's government.

Most noted amongst these was the Associate Minister of National Defence, Pierre Sévigny, who had seen her since 1958 and had even signed Munsinger's application for Canadian citizenship. The RCMP discovered her background, however, and informed Justice Minister E. Davie Fulton of her activities. She was deported to East Germany in 1961. The matter was dealt with behind closed doors and Sévigny resigned in 1963.

Traditionally in Canada, the personal lives of politicians are not discussed in parliament or in the media, but in 1966 the Liberal government was under attack for an unrelated security breach. On March 4, an angry Justice Minister Lucien Cardin rebutted the Tories by bringing up the Munsinger Affair in the House of Commons. The story dominated the media for weeks and was followed with rapt attention across the country. It became a massive distraction and all but shut down all other parliamentary activity for some weeks.

Munsinger was found living in Munich, despite the government insisting she had died of leukemia, and freely admitted her numerous affairs with government officials to the Canadian media.

A Royal Commission was eventually held that criticized the Diefenbaker government's handling of the case but found no criminal wrongdoing or security breach.

The newsmagazine series This Hour Has Seven Days was one of the major news organizations involved in covering the scandal, and when that series was cancelled by the CBC just weeks after the Munsinger Affair broke, it was believed by some observers that the show's dogged pursuit of the story had been one of the real reasons for its cancellation.