LONDON (REUTERS) - British Prime Minister Boris Johnson's plan to kick off what is in effect an election campaign casting parliament as the enemy of Brexit was overshadowed on Thursday (Sept 5) when his younger brother quit the government, citing the national interest.

As the United Kingdom spins towards an election, Brexit remains up in the air more than three years after Britons voted to leave the bloc in a 2016 referendum.

Options range from a turbulent 'no-deal' exit to abandoning the whole endeavour.

Ahead of a speech in northern England where the prime minister was expected to begin an informal election campaign, his own brother, Jo, resigned as a junior business minister and said he was stepping down as a lawmaker for their Conservative Party.

"In recent weeks I've been torn between family loyalty and the national interest - it's an unresolvable tension & time for others to take on my roles," he tweeted.

The prime minister's spokesman issued a statement thanking Jo Johnson for his service and adding: "The PM, as both a politician and brother, understands this will not have been an easy matter for Jo."

The 47-year-old has been in parliament since 2010, serving in several ministerial roles.

The move comes in a frenetic week for his older brother.

After wresting control of the lower house of parliament on Wednesday, an alliance of opposition parties and rebels expelled from Johnson's Conservative party voted to force him to seek a three-month delay to Brexit rather than leaving without a deal on Oct 31, the date now set in law.

Since taking office in July, Boris Johnson has tried to corral the Conservative Party, which is openly fighting over Brexit, behind his strategy of leaving the European Union on Oct. 31 at all costs, with or without a deal.

On Tuesday, he expelled 21 Conservative lawmakers from the party for failing to back his Brexit strategy, including Winston Churchill's grandson and two former finance ministers.

ELECTION LOOMS

Behind the sound and the fury of the immediate crisis, an election now beckons for a polarised country.

The main choices on offer are Johnson's insistence on leaving the EU on Oct 31, come what may, and Labour leader Jeremy Corbyn's hard-left socialist vision, coupled with a promise of a fresh referendum with an option to stay in the EU.

Already, the crisis has for three years overshadowed European Union affairs, eroded Britain's reputation as a stable pillar of the West and seen sterling twitch in tune to the probability of a 'no-deal' exit.

Asked if Brexit would happen on Oct 31, Johnson's belligerent senior adviser Dominic Cummings, a focus of many departing Conservative lawmakers' grievances, told Reuters:"Trust the people."

A spokesman for the prime minister said his speech would make the case that "it is now time for the people to decide after parliament has failed them, so we can resolve this once and for all".

"Jeremy Corbyn continues not only to block Brexit but is now also stopping the people having their say by refusing a general election."

The opposition Labour Party cast Johnson's language - including calling Corbyn a "chicken" - as pathetic, said he was trying to act like US President Donald Trump, and compared him to a 3-year-old toddler having a tantrum.

Against the dollar, the pound rose 0.7 per cent to US$1.2337 (S$1.71), after jumping 1.4 per cent on Wednesday on the sense that the prospect of a 'no-deal' exit had receded.

UBS Global Wealth Management said sterling could rally to US$1.30 if Brexit was delayed until January 2020 and an election was held after October.

"TRUST THE PEOPLE"

Johnson, the face of the 2016 Vote Leave campaign, has pushed for an election on Oct 15, two weeks before the United Kingdom is due to leave the EU, though opposition parties are debating which date they would accept.

"We are saying, yeah, bring on a general election, of course," said John McDonnell, the Labour Party's second most powerful man. "We will ensure that happens after we have got the legislation to protect against a 'no-deal' Brexit. But we will consult and do it on at the date on which we will think will have maximum advantage against a 'no-deal'," he said.

While sterling rose on parliament's bid to block a no-deal exit, an election before Brexit would allow him, if he won, to repeal the blocking bill, which was passed by 329-300 and then 327-299 in the House of Commons on Wednesday.

The law will pass the upper house, the Lords, by Friday evening.

Diplomats said an election campaign would halt any Brexit talks with the EU and expressed frustration with the turmoil in British politics at such an important juncture in European history.

"The UK side continues to produce chaos and it is very hard to predict anything," said one EU diplomat.