LONDON - 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 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 47-year-old, who campaigned to remain a member of the EU in the 2016 referendum while his older brother was the face of Vote Leave, has been in parliament since 2010, serving in several ministerial roles.

The move comes in a frenetic week for the premier, who said his brother had been "a brilliant, talented minister and a fantastic MP", and that the decision would not have been easy.

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.