The Government has introduced a law change that will allow bosses to withhold workers' regular breaks, and instead pay for the time or trade the breaks for time off later.

National's bill allows bosses to replace regular breaks with "compensatory measures".

These include being able to start work late or leave early, or stockpile the missed breaks and trade them for a day off.

The bill does not limit the forms of compensatory measures, so employers could pay staff rather than giving breaks.

Although the bill says there should be "good faith bargaining" between bosses and workers, it gives employers the final say over when and how long breaks will be if agreement cannot be reached.

Labour's employment spokesman, Trevor Mallard, said the bill contained downsides for vulnerable workers whose breaks weren't protected in collective contracts.

"The idea you could be pushed into taking no breaks at all and pushed into having them outside work hours is not a good idea.

"It means the break is worth nothing if it can be replaced with 'time off' at the whim of their employer."

Labour Minister Kate Wilkinson said the changes were aimed at restoring flexibility for employers, by allowing them to time breaks in a way that did not disrupt their businesses.

It is partly aimed at solving problems in workplaces such as sole-charge air traffic control watchtowers.

The bill will repeal the law passed by Labour last year which gave workers two 10-minute breaks and a half-hour lunch break at reasonably well-spaced times each day.

Before that, there was no statutory requirement for paid breaks, although most workers negotiated them as part of their employment contracts.

There has been little consultation over the proposed changes, although National has foreshadowed it.

The explanatory note to the bill says officials raised concerns about developing the changes "at speed and without adequate consultation".

Although Government departments were consulted, other parties, including Business NZ and the Council of Trade Unions, had not been.

The Employers and Manufacturers Association's employment services manager, David Lowe, said the law change would allow businesses to revert to the more practical custom they had used before last year's change.

"The current law assumes everyone has a cup of tea at 10am and 3pm and 30 minutes for lunch at 12 noon."

But Council of Trade Unions president Helen Kelly said last year's law was flexible enough to cater for different businesses while giving "the most vulnerable" protection.

The new bill replaces the minimum rest break lengths with the more general guideline requiring employers to give workers "a reasonable opportunity ... for rest, refreshment and attending to personal matters".