London-British Foreign Secretary Boris Johnson found himself in an awkward situation on Sunday after a confidential opinion piece, written by him in pro-Remain column in February, showed that he backed membership of the free trade zone, describing it as “a market on our doorstep, ready for further exploitation by British firms.”

Johnson had previously admitted to writing the pro-Remain piece but its contents had not been known until now – having been revealed in Sunday Times Political Editor Tim Shipman’s new book: All Out War.

In a newspaper column drafted in February, and now published by the Sunday Times, Boris Johnson suggested staying in the EU would be a “boon for the world.”

In the article, which was produced at the same time as a pro-Brexit article published in the Telegraph, Johnson also warned Brexit could lead to an economic shock, Scottish independence and Russian aggression.

He wrote: “There are some big questions that the ‘outside’ need to answer. Almost everyone expects there to be some sort of economic shock as a result of a Brexit.”

Johnson, now a proponent of a “hard Brexit” that would take Britain out of the European single market, put the opposite argument in his “remain” column.

“This is a market on our doorstep, ready for further exploitation by British firms. The membership fee seems rather small for all that access. Why are we so determined to turn our back on it?” he wrote.

Johnson defended his writing of a pro-EU article days before he publicly backed Brexit, saying the article was “semi-parodic” and the UK’s decision to leave was right.