Research conducted among more than 1,200 organisations by the non-aligned Institute of Employment Studies shows widespread ignorance of the law.
Charities representing the disabled believe businesses are letting themselves in for court action from prospective employees who have been rejected for jobs and current employees who believe they have suffered discrimination.
The IES report comes as a separate study by Unum, a US insurer, reveals that employers may face up to 3,000 industrial tribunal claims from disabled staff in the next 12 months.
Under the statute, workers can take action through the industrial tribunal system if they believe they have been subject to less favourable treatment; if they consider employers have failed to make "reasonable adjustments" for them, or if they think they have been victimised. The Act applies to all employers with 20 or more workers.
The remedies open to the tribunals are similar to those available in cases involving race and sex discrimination, although the disabled will have no statutory commission to back their cases.
The Royal National Institute for the Blind found in a survey that more than half of employers would not hire anyone who had "difficulty in seeing". The Institute argues that such organisations could face tribunal cases.
Because the disabled are not allowed legal aid to present their cases, some of Britain's top employment lawyers are prepared to waive their fees to take "strategic cases".
David Royle, director of marketing at Unum, said: "We believe the Disability Discrimination Act will catch many of the UK's employers off-guard. Our own research shows that two out of five haven't even heard of the new legislation, let alone started preparing for it."
Unum's prediction of the number of legal claims likely to be faced by UK employers follows the introduction of similar laws in the US in 1992. In the first full year of operation, more than 15,000 lawsuits were launched against employers.
More than half the claims were over allegedly unfair dismissal, with a further 28 per cent linked to failures by employers to provide a reasonable working environment.
However, two-thirds of all suggested workplace adjustments cost pounds 300 or less.
In an interview with People Management magazine, Robin Lewis, an employment specialist at Bindman solicitors said: "It is in the interests of everybody, including employers, that the first cases that are brought should be good cases that affect large organisations and have significant implications."
The recruitment specialist Scott Edgar reports that 57 per cent of personnel managers in large British companies say the Act will discourage particularly small companies from taking on disabled applicants. Some 43 per cent of respondents in the survey, however, believed the law did not go far enough.
There was confusion over a definition of disabled employees and whether stress-related illnesses would be included.