Workplace relations at the Bureau of Meteorology (BOM) are cold and the forecast is for increasing frost.

BOM staff have stepped up their campaign in protracted pay negotiations, hijacking the weather bureau's website and media appearances with messages about the dispute.

Melburnians checking the weather forecast on the bureau's website or mobile app this week may have seen this message, before it was quickly taken down:

A message from BOM staff on the Weather Bureau's app is interspersed with the daily forecast. ( ABC News )

"Mostly cloudy. Areas of morning fog. Patches of light early morning frost in the Yarra Valley. Light winds. Bureau staff have been fighting for years to hold on to the conditions we have, but they are under attack," the forecast said.

"This five year pay freeze — while we defend our allowances and conditions — is hurting us and hurting our families. We love the work we do, we know you value it too. Please support us to get a fair deal."

Some meteorologists giving live weather reports on radio programs have also prefaced their forecasts with details of the pay dispute.

It follows a series of smaller acts of subversion by Bureau of Meteorology staff to draw attention to their social media campaign with #5yearpayfreeze and #BOMonStrike

The Community and Public Sector Union (CPSU) has defended the tactics.

"It is not the first thing we leapt to, but after five years without a pay rise and four years in a protracted dispute we're keen to let people know how tough the bureau workers are finding it," CPSU Deputy Secretary Beth Vincent-Pietsch said.

"Our members have never compromised on the quality service that they provide.

"They're not NOT providing the forecast, they're providing the forecast with a #BOMonStrike.

"We've had a positive response so far."

Ms Vincent-Pietsch said management at the BOM had been trying to shut down the campaign efforts, "even though it's protected industrial action".

"It has been authorised by Fair Work Australia, so our members can legally do it."

Perth forecast includes message from BOM staff over pay dispute. ( ABC News )

In a statement, the BOM said it "respects the rights of union members to take protected industrial action".

"The Bureau has a responsibility to ensure that its products and services, including its forecasts and warnings, are not compromised.

"The Bureau is putting various measures in place to meet that responsibility and to maintain the standard of its products and services."

The Ms Vincent-Pietsch is determined that will not stop the campaign.

"Union members are pretty determined and creative … it's pretty hard for management to stop it altogether."

After five-year pay freeze, negotiations labour on

The last enterprise agreement expired in 2014 and three attempts to strike a new deal since then have failed.

In the meantime, pay for the bureau's 1,600 staff has been frozen at 2014 rates.

A fourth offer is being put to staff and voting on whether to accept the deal will close next week.

The (CPSU) is urging bureau staff to vote 'No', arguing it it still sub-standard compared to pay deals offered to employees of other government agencies.

"Largely, the issue doesn't come down so much to pay as it does to the attack on workers conditions and rights," Ms Vincent-Pietsch said.

"We've clawed back a lot of things that were looking at being axed … protections for shift workers … a lot more protection for people around their hours, allowances for remote localities, allowances for people who work out in the field have been improved.

"But it's still not as good as what other agencies have been able to achieve.

"It's frustrating, because management could shift more."

The BOM told the ABC the proposed agreement "provides a substantially front-loaded pay increase, protects core conditions, is financially sustainable and complies with the government's Workplace Bargaining Policy".

"It enables the bureau to continue to provide the critical services we provide to the Australian community in an affordable, sustainable way.

"The proposed new Enterprise Agreement follows ongoing negotiation in good faith with staff and unions."