Townsend turns down B&I Lions
The end of the current European season will see the highly-regarded Glasgow boss succeed Vern Cotter as coach of Scotland.
Former Scotland playmaker Townsend had long been tipped for a role in Lions chief Warren Gatland's coaching team.
But with the Lions' tour clashing with Scotland's series in Australia, Townsend has put his country ahead of the combined side.
"It's a case of timing," Townsend told the Scottish Rugby Union website on Thursday.
"I feel hugely privileged to be given the Scotland job and our first opportunity to work with the players is at the same time as the Lions tour.
"I was approached [by the Lions] a couple of weeks ago – and I was obviously flattered – but my priority now is Glasgow and at the end of the season Scotland are going on tour, so that's the priority then."
He added: "I had a good think and didn't give an immediate answer. I really wanted to reflect on what was involved but I quickly realised that the Scotland tour to Australia is my number one priority at the end of this season.
"At international level you don't get that much access with the players. This is the most access you'll get with them.
"On a tour you get to work with them, preparing them and spending time with them, so that's the biggest factor," Townsend explained.
Gatland, bidding to guide the Lions to just their second series win against his native New Zealand, is due to announce his coaching team on Wednesday.
Agence France-Presse
