She slapped down the Labour leader's campaign to "make Britain the best place to work," saying everyone except those employed by the party stands to benefit from his proposals. The opposition party's package includes calls for more rights for workers and a higher living wage.
Sir Keir tweeted: "Family incomes have stagnated, millions are in insecure work and in-work poverty is at a record high.
"Covid has brutally exposed the injustices that have been growing for years."
He said his plan would make the UK the greatest place to seek employment and offer a much-needed boost to Britons.
But Ms Abbott shot down his bid to gain public support, responding to the tweet by saying: "So Keir will make Britain the best place to work - unless you work for @UKLabour.
"He has made 90 staff redundant.
"But is also recruiting workers on insecure temporary contracts with worse employment conditions."
Her view on the issue appeared far more popular among social media users, who gave her more than 3,600 retweets and 10,400 "likes".
Sir Keir's tweet was retweeted by just 677 Twitter accounts and "liked" by 2,850.
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Corbynite Ms Abbott, a former shadow home secretary, was not the only one to disapprove of Sir Keir's latest plan.
Financial journalist Matthew Lynn said it showed Sir Keir "hasn't got a clue about modern jobs".
Writing in The Telegraph, he said neither the Labour leader nor his party appears to have grasped the major changes employment in the UK has undergone in recent years.
He added: "Work is changing rapidly already, in some ways for the better, although there will be lots of disruption along the way – but until Labour notices, no one is likely to listen to its rehashed plans for more legislation."
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Last week it emerged that dozens of Labour employees are facing the axe as the party's leadership scrambles to deal with a financial crisis.
The party has also faced criticism for hiring an agency on temporary contracts to work on the backlog of internal complaints.
A former aide to Jeremy Corbyn told the Big Issue: “Not only is this a bad look to the electorate, which doesn’t stand for hypocrisy, but what does it say about Labour under Starmer that it treats its own workers like this?
“While at the same time, the party takes on dozens of agency staff to deal with complaints.
"The root of all this is chronic mismanagement from people whose brains are infested with factionalism.”
Sir Keir set out sweeping proposals in his plan to improve working conditions for people in the UK.
He said security at work is of paramount importance and therefore "we would immediately outlaw fire and rehire" and "offer a new right to work flexibly and strengthen our trade unions".
He also said in order to buy and sell more within the UK, rather than looking overseas, Labour would "deliver investment in high-quality, well-paid green jobs in the industries of the future."
And he said a Labour government would "create tens of thousands of apprenticeships by ending the Treasury raid of the apprenticeship levy" to offer youngsters more opportunities as they enter the workforce.
He paid tribute to his humble background in a bid to garner support for his plan.
Sir Keir said: "My mum was a nurse. My dad was a toolmaker. Their working lives were hard – often harder than they should have been.
"But I saw how proud my dad was of his trade. How devoted my mum was to the NHS. And how their work gave them the opportunity to start a family.
"But after a decade under the Conservatives, modern Britain is not working for working people."