Culture Secretary Nadine Dorries confused the two rugby codes in a speech at a Rugby League World Cup event in St Helens on Thursday.
Dorries thought Jonny Wilkinson's 2003 winning drop-goal for England against Australia in rugby union's World Cup final took place in rugby league.
"I've always quite liked the idea of rugby league," Dorries said in her speech.
"My long-standing memory is that 2003 drop-goal."
She added: "We were drinking Bloody Marys at the time. Wow, what a moment that was."
She later addressed her mistake on Twitter.
"Like Jason Robinson I may have switched codes in my speech," she wrote.
"Both league and union have a rich heritage in the UK. Obviously I've followed rugby league much less in my lifetime, but I'm looking forward to watching England (and all the home nations) in the RL World Cup this autumn."
Rugby league and union have separate rules, points systems and team sizes - 15 players in a union side, and 13 in a league side.
Dorries had been speaking at the launch of an interim report into the World Cup's social impact programme, which is investing £25m into communities across England.
Rugby League World Cup chief executive Jon Dutton said the secretary of state had "clearly made a mistake" but added he was delighted she was there to support the launch of the report.
"The sport is 127 years old but needs a tournament like this to have more visibility. We want more people to be educated on what a wonderful sport rugby league is - and also, what a wonderful sport rugby union is," he said.
"We've had a conversation and we look forward to her coming to the tournament."
Billy Vaughan, vice-chairman of Portico Vine rugby league club in St Helens where the event took place, said: "I thought it was comical.
"No detriment to her, somebody writes that speech for her, they just need to do their research. It's a little bit disrespectful to the various codes and there's a big difference in the codes."