Dominic Cummings has resigned as Johnson's most powerful aide and will vacate his office by end of the year, a source with knowledge of the matter said.
Cummings has been at Johnson's side since he took office in July last year, and was the brains behind the successful Brexit referendum campaign that catapulted Johnson into the front lines of British politics three years earlier.
Experts say that his departure will be detrimental to Johnson's leadership as it faces a pandemic and navigates the closing phases of Brexit. The 48-year-old Cummings is the prime minister's most important adviser and strategist. Johnson only has a few days left to iron out a Brexit trade accord with the European Union before it's too late.
Cummings' resignation came after Johnson's senior media adviser Lee Cain announced he was standing down as the prime minister's political communications chief Wednesday evening. Cain and Cummings were the prime minister's two closest aides and he will feel their absence.
Meanwhile, British Prime Minister Boris Johnson already refers to incumbent U.S. President Donald Trump as the former president of the country -- as Trump continues to go into denial and refuses to concede defeat to president-elect Joe Biden,
In a speech at the House of Commons on Wednesday, Johnson referenced the incumbent Trump as the "previous president" after he congratulated president-elect Joe Biden on his victory, The Hill reports.
An ally of Trump, the British prime minister told Parliament members about an "excellent conversation" he had with Biden on Wednesday. He said it was "refreshing" to hear Biden's view on immigration, climate change, free trade and international institutions, in an apparent jab at Trump's dislike of international organizations like the World Health Organization and NATO.
