LONDON - British Foreign Secretary Boris Johnson on Wednesday tried to shed more light on Britain's "road to Brexit," saying that stopping Brexit from happening would be a "disastrous mistake."

In his speech, titled "Road to Brexit -- a united Kingdom," Johnson said that "derailing Brexit would be disastrous." His speech was seen as an attempt to unite former Remain and Leave voters behind a liberal, optimistic view of Brexit.

Holding another referendum on the UK's membership of the European Union (EU) would be a "disastrous mistake that would lead to permanent and ineradicable feelings of betrayal," said Johnson, who was one of the leading figures in the 2016 Leave campaign.

Brexit should not be seen as an economic threat but as a great opportunity for the UK, he said.

Leaving the EU is "grounds for hope, not fear," he said, adding that Brexit is going about going global.

Brexit is not un-Britain, but internationalist, he said.

"Our commitment to the defence of Europe is unconditional and immovable," the foreign secretary said.

Johnson's address is the first of six speeches about Brexit by senior British ministers in next weeks as British Prime Minister Theresa May prepares to outline her vision of Britain after it leaves the EU.

Two other leading Brexiteers in the cabinet, international trade secretary Liam Fox and Brexit secretary David Davis, will also deliver speeches over the next two weeks.

David Lidington, May's de facto deputy and a former Remainer, will speak about Brexit and devolution.

The prime minister will speak at the Munich security conference next Saturday when she is expected to propose a new security partnership with the EU.

Some British ministers hope to remain part of Europol and the European Arrest Warrant after Brexit, although the latter is anathema to hard Brexiteers because it involves the jurisdiction of the European Court of Justice.

May is expected to make another speech about Brexit towards the end of this month, after she and her senior ministers spend a day outside London discussing Britain's negotiating position on its future relationship with the EU.