The cash-strapped bureau says a "front-loaded pay offer that will give workers a 6 per cent increase in the first 18 months is the best staff can hope for.

But the forecaster's 1600 public servants have not had a payrise since 2013 and their main workplace union says the bureau's offer will leave some of its workers more than $6000 worse-off each year.

The Community and Public Sector Union says the proposed workplace agreement presents a clear threat to the quality of the bureau's weather forecasts by making it harder to hold on to its best technicians.

But the bureau, which concedes it must pay for the pay rises partially through not replacing it departing public servants, is broke.

Its 2016 accounts show a $76 million loss, an even worse result from the $52 million it haemorrhaged in 2015.

But the union says the BoM is one of the "hold-out" public service agencies, still determined to impose the harsher aspects of the Abbott-era industrial relations policy that has softened recently in some big departments.

A bureau spokeswoman confirmed the agency's proposed deal was "consistent with the Australian government's workplace bargaining policy".

"It offers staff a 6 per cent salary increase payable in the first 18 months and retains key entitlements including rates of superannuation contribution, current weekly hours of work, personal/carer's leave and pregnancy, parental and other carers' leave entitlements," she said.

"The pay rise would mostly be funded through careful consideration of recruitment following staff resigning or retiring from the organisation, and careful consideration of non-ongoing contracts.

"Other proposed changes to fund the pay rise include changes to how staff book and pay for travel, salary advancement, travel allowances and changing some allowances available for staff in locations currently classified as 'remote' and are now considered 'outer regional', in line with the ARIA classification used by other APS agencies.

"The proposed enterprise agreement represents the highest possible pay offer available to APS staff."

But the CPSU says it expects bureau staff, who rejected a proposal from their bosses in February 2016 by a bruising 69 per cent, to send a similar message this time.

"It's disappointing that Bureau of Meteorology management [is] pushing such a harsh agreement at a time when the majority of enterprise negotiations across the Commonwealth public sector are moving in the opposite direction," the union's Secretary Beth Vincent-Pietsch said:

"Frontline staff doing essential work in remote locations and rostered around the clock are still facing deep cuts to their take-home pay, with some staff to have up to $6000 stripped out of their annual pay packets.

"Just as concerning is the attempt to scrap family-friendly rights so staff can ensure their roster isn't causing unreasonable strain on the home front."

"We believe this draft agreement is a threat to the quality and reliability of BoM's critical forecasting services, because such harsh cuts will inevitably make it more difficult to retain and attract quality frontline staff."