Bus operator Tower Transit said it "inadvertently" hired more bus captains than it needed between December and January, during its recruitment activities.
Six had already signed employment contracts with the Anglo-Australian firm when they were told the offers were being rescinded.
One bus captain was informed by e-mail just two weeks before he was due to start work this month that the company had reached "full staff capacity" and was "unable to proceed" with its job offer.
The man, who did not want to be identified, said the recruitment drive was "misleading" and that those who had quit their previous jobs after getting offers were "left stranded and distressed".
A Tower Transit spokesman told The Straits Times the company has since tried to help the men who were affected.
"It's a situation that has caused them distress, and we're doing everything we can, including direct referrals to other organisations, to help them find similar positions," he said, adding that only three had responded to the offer of help.
The Ministry of Manpower (MOM) said Tower Transit had acknowledged "lapses" in its human resource process and told the ministry it would compensate the affected parties, though no details were given of what this would be.
"Affected individuals who have any queries may approach MOM or the unions, if they are union members, for advice and assistance," said a ministry spokesman.
Both employers and employees should commit to the terms and conditions of the employment contract once it is signed, said Mr Melvin Yong, executive secretary of the National Transport Workers' Union (NTWU). "If either party has to revoke the contract, due notification, explanation and compensation should be given," said Mr Yong, who is also a Member of Parliament for Tanjong Pagar GRC.
He added that the NTWU can help affected employees by linking them up with the Employment and Employability Institute for job placement assistance.
Tower Transit's willingness to try and find alternative jobs for the affected parties does not "detract from or waive its breach" of the employment agreement if it did not comply with the provisions surrounding its termination, said lawyer Vernon Voon.
The employment and labour relations partner at law firm RHTLaw Taylor Wessing noted: "In the event that an alternative job is offered, that will only go towards mitigation of the damages that the affected parties have suffered as a result of the company's breach in not observing the terms of the agreement regarding its termination."
Tower Transit became the third public bus operator here in 2015.
• Additional reporting by Adrian Lim