An Australian couple were unwittingly conned into becoming multi-million dollar drug mules after winning a dream trip to Canada with new luggage thrown in.

The elaborate con duped the couple by taking them to Canada as the winners of an all-expenses paid trip, which included accommodation and new suitcases.

But after a dream week in North America, the couple became suspicious about their bags on their return to Western Australia and reported themselves to customs.

Officials discovered 3.5kg of methamphetamine in crystal form in each of their cases, worth a total of £4.1m.

The 64-year-old woman, who wanted to be known only as Sue, said they had been looking for a holiday online and were contacted and after entering an competition.

"Be very careful if you win anything," she said. "I could have ended up in jail for 25 years, and they could have ruined my life. So be very wary, be very careful and check everything out."

Police believe their luggage was swapped while in Canada, with the couple having no clue they were then being duped into carrying the drugs home.

The couple were due to be met on arrival, which set the course of a police investigation that led to a search warrant being issued for a car and a room in Perth, where documents related to the con, more bags similar to the ones seized and nearly £9,000 in cash were found.

A 38-year-old Canadian man was arrested at Perth airport, and has subsequently been charged with drug trafficking offences.

David Bachi, the Perth Airport police commander, said the alleged scam was one of the most elaborate federal officers had come across.

"The organisers of this scam went to great lengths to provide a facade of legitimacy. Thankfully the travellers contacted customs and didn't dismiss their concerns, allowing us to make the arrest," he said.

"We will continue working with local and international law enforcement partners, targeting all elements of this drug syndicate."

Bachi said the scam, operated through a bogus Canadian tour company called AusCan Tours, appeared to be targeting older Australians.

The Canada-based website has now been shut down.