Foreign Secretary Liz Truss and former Chancellor Rishi Sunak are facing off as the final two contenders to take over as the next Tory leader.
Over the coming weeks, it will be up to party members to decide which of the two takes up residence in Downing Street.
Ms Truss and Mr Sunak will take part in a televised leadership debate on Monday evening, as the campaigns become increasingly bitter.
But it is the issue of austerity that has attracted particular criticism from Ms Abbott, as she hit out at both candidates.
Diane Abbott was very critical of Ms Truss and Mr Sunak PA
She wrote on Twitter: "One contender thought it was a good idea to impose more austerity during a cost-of-living crisis.
"The other applauded him, but now attacks him from the right.
It came as the two leadership rivals clashed over the former Chancellor's vow to "get tough" on China.
Mr Sunak has promised to close all of the communist state's 30 Confucius Institutes in the UK.
Foreign Secretary Liz Truss Aaron Chown
Former Chancellor Rishi Sunak Dominic Lipinski
The institutes are funded by the government in Beijing. They are intended to be culture and language centres – but critics argue they embody Chinese propaganda tools.
Mr Sunak accused China of "propping up Putin's fascist invasion of Ukraine", "stealing" British technology and "infiltrating our universities".
He pledged to lead the world in standing up to China's "technological aggression" by amending the Higher Education Bill to force British universities into disclosing foreign funding partnerships of more than £50,000.
The 42-year-old added: "I will stop China taking over our universities, and get British companies and public institutions the cyber-security they need.
"And I will work with President Biden and other world leaders to transform the West's resilience to the threat China poses."
Hitting back, a spokesman for Ms Truss's team accused the former Chancellor of being "soft" on China, pointing to an article in Beijing's Global Times that "effectively endorsed" Mr Sunak as their preferred candidate.
The spokesman added that Ms Truss, during her tenure as Foreign Secretary, has "strengthened Britain's position on China" and "helped lead the international response to increased Chinese aggression".
Former Tory leader Sir Iain Duncan Smith, who backs Ms Truss's campaign, asked Mr Sunak: "After such a litany, I have one simple question: 'Where have you been over the last two years?'"