Britain has a lot of work to do before triggering the formal divorce procedure with the European Union but once it is done, the country will not let the process drag on, Foreign Minister Boris Johnson said on Sunday.

Last week, Johnson said Britain would trigger Article 50 of the EU's Lisbon Treaty to start its exit from the bloc early next year. He was swiftly put in his place by Prime Minister Theresa May's aides who said the policy was the same — Britain would not invoke the procedure this year.

"I think the crucial thing is that obviously we are not going to do it before Christmas and I think we've got to do a lot of work to get our ducks in order and that is going on," Johnson told the BBC's Andrew Marr program.

"But then after that, as the prime minister has rightly said, this process probably shouldn't drag on."