By Marc Jones and Huw Jones
LONDON (Reuters) - Luxembourg's Prime Minister Xavier Bettel on Wednesday urged Britain to accept the rules of EU single market or face a potential cliff-edge exit in a year's time.
Speaking at a London School of Economics event during a trip to a NATO summit near the UK capital, Bettel said he respected Britain's decision to leave.
British Prime Minister Boris Johnson has said that if he wins in the general election on Dec. 12, he will take Britain out of the EU on Jan. 31.
Johnson has said he can negotiate a new trade agreement with the EU by the end of 2020, when a transition period ends, but sceptics say Britain may need more time.
Bettel cautioned that Britain could not pick and choose what it wants from the EU. Johnson has said he does not want Britain to be part of the single market and accept obligations such as the free movement of people.
"The fact is we cannot accept cherry-picking, the fact is you decided to leave," Bettel said.
"I won't accept that we destroy the single market. We have rules and you will have to accept these rules."
Much could hinge on whether Johnson wins a big enough majority in the election to push through the divorce settlement he has negotiated with Brussels, Bettel said.
Brexit was becoming a "poison" for society and Britain's citizens wanted certainty. "(On Brexit) They want you to deliver, they want an answer what is going to happen tomorrow," he added.
A new European Commission began work this week in Brussels and Bettel said it was important that the bloc remains competitive in the world.
On the strength of NATO, following candid footage of Canadian Prime Minister Justin Trudeau laughing at lengthy press appearances by U.S. President Donald Trump, Bettel said: "I think we (NATO) are much more united than it looks."
Also quipping, Bettel said his chief of staff often reminds him "don't speak even if you know nobody is listening".
(Reporting by Marc Jones and Huw Jones; Editing by Giles Elgood)