The figure was reported by Sky News, who credited an inside source at the supermarket giant.
Contracts and letters revealed to JPIMedia by an anonymous Asda employee state that any staff member who has not signed and agreed to the new terms by the 2 November deadline will lose their job.
Workers that have turned down the new deal are currently serving notice periods, however they have been told that they can change their minds.
The new deal, called Contract 6, sees paid breaks scrapped and bank holiday work made compulsory, in exchange for a £9 per hour basic rate.
Previously the contracts had been voluntary, however letters issued in August this year informed employees that the new terms were compulsory if workers wanted to remain employed by Asda.
The announcement sparked a protest from workers, which took place on 14 August.
March on Asda headquarters delivers petition
Yesterday (16 Oct) hundreds of workers travelled from around the country and marched on the Asda headquarters in Leeds to deliver a 23,000-strong petition against the new contracts.
Asda said on Wednesday that the "vast majority" of over 100,000 people affected by the new contract had agreed to the new terms.
And in August spokesperson for Asda clarified that, although the new contracts meant employees would have to work most bank holidays, Christmas Day, Boxing Day and New Year’s Day would remain voluntary and staff working on those days would receive double time.
In April, the supermarket said that it had entered consultation with employees over the new contracts, and that 50,000 employees were already on them.
The grocer admitted five per cent of workers would be worse off under the changes but said “transitional payments” would be in place for these employees for up to 18 months.
The move by Asda follows a similar decision by rival Sainsbury’s, which last year made the decision to axe paid breaks. The supermarket, which is owned by US retail giant Walmart, says the contract increases the take-home pay of more than 100,000 employees through an investment of more than £80m.
"We understand that change is never easy, but we are determined that Asda remains a sustainable business for its customers and colleagues - now and in the future," a spokesman said.
But Union GMB has called the proposed contract changes “punitive” and said that workers stand to lose out on hundreds of pounds a year. It also said that in a ballot of union members, 93 per cent of workers said that they were not happy with the new contracts they were being asked to sign.
Gary Carter, GMB National Officer, said, “We're calling on Asda to come back to the negotiating table and give this dedicated workforce a fair deal.
“This demonstration will send a loud and clear message to Asda that however much pressure management has put on staff to sign, workers believe contract 6 is still not good enough.
“Asda is a multi-billion pound, highly profitable company - it can afford to treat staff better than this.
“The new contract cuts holiday entitlement, slashes bank holiday and night shift pay, and introduces an any time, any place, anywhere culture which risks a hugely damaging impact on the predominantly part time, low paid, female workforce, who need flexibility that works for them.”