Ms Hall liked an image of the notorious anti-immigration politician, a favourite of the far-right, which quoted him saying: “It’s never too late to save your country.”
The tweet liked by the Tory hopeful bore the message: “It’s never too late to get London back!”
The slogan by Powell – infamous for his “rivers of blood” speech which condemned immigration to Britain – was used by the British National Party (BNP).
Ms Hall was also found to have liked a message on X, formerly known as Twitter, which described Mr Khan as “our nipple height mayor of Londonistan”.
Further tweets liked by Ms Hall, first highlighted by The Times, included one suggesting that Mr Khan would endorse corruption at May’s mayoral vote.
The post claimed the Labour mayor was “begging for londoners to do a tower hamlets postal vote for May next year and we all know how that works. #fraud”.
Following a tweet in which Ms Hall criticised Mr Khan’s strategy for tackling violence against women and girls, she liked a response which said: “Well said Susan, that Labour Traitor RAT likes that sort of thing.”
A spokesperson for the Hall campaign said: "Susan engages with many people on Twitter without endorsing their views.
“Londoners want a mayor who listens to people and deals with the bread-and-butter issues that matter to them – making our streets safer and putting more money back in people’s pockets. As mayor, Susan will deliver that.”
Georgie Laming, director of campaigns at HOPE not hate, called on the Tories to suspend and remove Ms Hall as the candidate. “The Conservative Party is putting up a candidate who has shown her endorsement of Enoch Powell. Susan Hall is not fit to represent London and all its diversity.”
The right-winger with a history of controversial views emerged as the surprise candidate for the Tories earlier this year after former minister Paul Scully failed to make the shortlist and Daniel Korski pulled out after being accused of groping.
Ms Hall has branded the Notting Hill carnival “dangerous” and said the Black community has a “problem with crime”.
Opponents have also highlighted her backing for Liz Truss’s ill-fated mini-budget, as well as her comparison between Donald Trump supporters storming the US Capitol and Remainers refusing to accept Brexit.
Conservative chiefs have launched an internal review of the party’s operation in London after she emerged as the candidate. Tory chairman Greg Clarke said it was “being done with the full support of Susan Hall”.
A bombshell survey last week found that Ms Hall is set to defeat Mr Khan – if left-winger Jeremy Corbyn joins the race as an independent.
The former Labour leader – blocked from standing for the party at the next general election – has refused to rule out running in the contest in May.
Mr Corbyn would get 15 per cent of the vote, according a Redfield and Wilton Strategies poll. But in doing so he would split the vote and hand victory to Ms Hall – on 30 per cent with Mr Khan on 25 per cent.
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