The activist and journalist attended the annual UNICEF Halloween Ball dressed as Melania Trump being groped by her husband, the Republican presidential nominee Donald Trump.

"'Grab 'em by the pussy' #yourworstnightmare," she posted to Instagram ahead of the star-studded event in London.

Her uncanny appearance was offset by some severe smoky eyeshadow, a form-fitting white dress and a blow-up doll resembling Trump wrapping his arms around her.

"Donald, you can always grab me if you like," she said in a video posted to her 26,000 fans, doing her best Melania impression.

In a later, more disturbing frame, she cuddled up to the doll and mouthed "I love him" while a friend looked on in alarm.

Khan's costume also took aim at Mrs Trump by carrying a stack of papers on the red carpet titled: "Michelle Obama's Convention Speech".

She completed her sartorial sledge with a Trump placard that included a reference to his recent election date gaffe: "Make America great again! Trump 2016. Vote on 28th November!!!"

The US election is on November 8.

The activist has a keen interest in politics.

During her nine-year marriage to cricketer-turned-leader of the Movement for Justice Party in Pakistan, Imran Khan, she campaigned for an end to corruption for in the country.

She also set up a (now defunct) fashion label specifically to raise funds for the Shaukat Khanum Memorial Cancer hospital.

The 42-year-old returned to Britain after her divorce in 2004 and is now a contributing European editor of Vanity Fair and associate editor of the political publication, New Statesman.