Many employers will be made to reveal how much male staff are paid compared with their female colleagues, under a bill being published later.
The Equality Bill aims to tackle discrimination against a range of groups including women, the elderly and those from lower social classes.
It will also make it a legal duty of public bodies in England and Wales to address social inequalities.
The Conservatives have described the plans as "class war attacks".
Minister for Equality Harriet Harman pledged the bill would help to "narrow the gap between rich and poor and make Britain more equal".
The result of this [bill] will mean that it will take longer to get out of recession and companies will be loathe to take on more employees
British Chambers of Commerce
Ministers say the need for new measures is borne out by evidence showing that by the age of six, bright children from poor families are overtaken by less able children from wealthier homes and that people in deprived areas tend to suffer more from ill health.
The government had promised the bill, which will also ban age discrimination outside the workplace, in its manifesto before the last election.
Ministers also want to tackle the fact that - 40 years after the introduction of the Equal Pay Act - women in the UK still earn on average 23% less per hour than men.
The new bill will require companies employing at least 250 staff to publish their gender pay gaps by 2013. If too few have done so voluntarily, the government will use laws to make it happen.
'Struggling to survive'
However, business leaders have criticised the measures, saying small firms are already struggling to cope with a "mass" of employment law.
Miles Templeman, director general of the Institute of Directors, said: "This is a further example of unnecessary regulation at a time when companies, particularly small and medium-sized enterprises, are struggling to survive."
There is no excuse for having unfairness when times are difficult
Minister for equality
David Frost, director general of the British Chambers of Commerce, will tell its annual convention on Monday that the government too often sees the answer to a problem as being more legislation.
"The result of this will mean that it will take longer to get out of recession and companies will be loathe to take on more employees," he will say.
But Ms Harman said there was "no excuse for having unfairness when times are difficult".
"The economies and societies which will prosper in the future are not those that have rigid hierarchies, where women know their place and where you can't go forward because of the colour of your skin," she said.
"That's a very backward-looking argument."
Another of the bill's controversial goals is to ban age discrimination.
Ministers want older people to pay for services, such as insurance, based on the actual risk they face, rather than an arbitrary age-based cost. This has the backing of charity Age Concern and Help the Aged.
However, the Association of British Insurers has denied its members' policies are unfair, saying they simply take account of risk.
The bill will also give public bodies in England and Wales, including councils and health authorities, a new "social economic duty" - something that is already done in Scotland.
For example, health trusts will be required to target services, such as stop-smoking clinics, at people in deprived areas - where smoking rates tend to be higher.
Education authorities will also be expected to come up with policies which prevent children from poorer backgrounds from missing out on places at the best schools.
However, Ms Harman has insisted the bill will not mean working-class people are given precedence in job applications or on waiting lists for services.
The Conservatives have previously attacked such measures as "missing the point".
Shadow work and pensions minister Theresa May said earlier this year: "You don't make people's lives better by telling them they have a legal right to a better life.
"You do it by tackling the root causes like family breakdown and poor education."