Boris Johnson demands a great Brexit from Theresa May

Boris Johnson condemns Theresa May's fog of self-doubt as he calls for policy u-turn from the British leader

FILE -Ex-Foreign Secretary Boris Johnson (AP Photo/Frank Augstein, File)

Boris Johnson, the face of the Brexit referendum who resigned as foreign secretary in protest at Theresa May’s proposal for leaving the EU, warned her government must reverse course to seize the last chance for a clean exit from Europe.

In a much anticipated speech, Mr Johnson attacked the prime minister's approach but said she could still command support for her leadership. The former journalist warned that her proposal for a new relationship with Europe was a "miserable, permanent limbo".

"It is not too late to save Brexit. We have time in these negotiations, we have changed tack once and we can do so again," he told the House of Commons as his supporters crowded the nearby benches to show support.

"We must try now because we will not get a chance again."

The short statement was far from the dagger to Mrs May's career that had been speculated on. Before his appearance there had been parallels drawn with a speech in similar circumstance in 1990 by Sir Geoffrey Howe, another former foreign secretary, that destroyed the career of Margaret Thatcher.

In his resignation letter Mr Johnson said Mrs May’s Brexit strategy killed the “dream” of breaking free from the European Union. Expanding on the theme on Wednesday, he said Britain would be left in a state of economic vassalage with no power to initiate, innovate or deviate outside EU trade standards.

Mrs May narrowly survived a crunch Brexit vote in parliament on Tuesday, defeating an amendment introduced by its own backbench MPs to a future trade policy bill. The measure would have kept Britain in a customs union with the EU if it fails to agree a free trade deal.

Mr Johnson used that victory as the pivot of his argument, asserting there was no majority in parliament for staying in an EU customs union.

Mrs May is battling to unite her Conservative Party around her Brexit blueprint formally unveiled last week following months of cabinet infighting. It would see Britain ask the European Union for a free trade area for goods through a "facilitated customs arrangement" alongside a "common rulebook".

If the amendment had passed it would have thrown May's Brexit strategy into disarray and increased pressure on the already beleaguered leader.

Brexiteers believe that keeps Britain too close to the EU, while pro-Europeans think it fails to protect the country's dominant services sector, among other gripes.

The backlash has seen the prime minister face persistent rumours her MPs are planning to topple their leader.