WASHINGTON—Sen. Kamala Harris is proposing that large employers pay women on an equal basis with their male counterparts or face government fines, seeking a sweeping shift in the way the nation addresses pay inequity.

The Democratic presidential candidate released a plan Monday that would put the burden on companies to demonstrate that they are not engaging in pay discrimination. Ms. Harris’s campaign said companies would be fined 1% of their profits for every 1% wage gap they allow to continue for work of equal value.

The campaign estimated that the plan would generate about $180 billion over 10 years, with revenue decreasing over time as equal-pay practices become more common.

Previewing the plan at a Los Angeles rally Sunday, Ms. Harris said she would make a national priority of “closing that pay gap and holding corporations accountable for transparency.” She warned, “There will be penalties if they don’t.”

Women who work full-time are paid 80 cents on average for every dollar paid to men, and the disparity is higher for black and Hispanic women. Under the Lilly Ledbetter Fair Pay Act, signed by President Obama in 2009, employees had an expanded time window in which to file gender-pay-discrimination complaints.