There is no doubt Britain's departure from the European Union means it will also leave its customs union and single market, Foreign Secretary Boris Johnson told reporters on Friday.
Last week, a vote in the House of Lords to amend a key piece of Brexit legislation threatened to complicate Prime Minister Theresa May's efforts to negotiate Britain's departure from the bloc.
But Johnson, who was one of the most visible pro-leave campaigners ahead of the 2016 Brexit referendum, insisted that May had made the position clear.
"The UK is coming out of the EU," he told reporters on the sidelines of a G7 ministerial meeting in Toronto.
"It doesn't mean we're coming out of Europe but it does mean that we need to change our relationships with the institutions of the EU," he said.
"And it clearly means that we're coming out of the customs union, coming out of the single market."
Last week, Britain's un-elected upper house, which is more skeptical of the case for leaving the European Union than the elected House of Commons, voted to require ministers to explain the steps taken to negotiate Britain's continued participation in a customs union.
But pro-Brexit politicians have denounced the move as an attempt to derail legislation designed to reflect the popular will expressed in the June 2016 referendum.
The legislation sets the legal framework for Britain's exit from the bloc on March 29 next year.