UNIONS are misleading shearers and causing problems for farmers over changes to the 40-hour working week, a Victorian farm leader says.

Victorian Farmers Federation industrial association president Alan Bowman says a campaign of misinformation by the Australian Workers' Union is a "disgrace".

The AWU was making it difficult for farmers employing shearers, by telling shearers that a 38-hour working week was about to come into effect across the whole industry, Mr Bowman said.

In fact, only wool growers operating as companies would be subject to new 38-hour working week provisions under new federal Fair Work laws, he said.

Unincorporated growers, who made up most of the industry, would continue to operate under a 40-hour week until the start of next year.

"The AWU has muddied the waters again in relation to shearers' working hours and pay," Mr Bowman said.

"All farmers want to provide for their employees is a fair day's wage for a fair day's work. Peddling mis-information about what changes are about to take place is hindering their ability to do so."

Under the changes, which begin on Friday, incorporated wool growers will still be able to request a shearing team to work for 40 hours, but can not force them to do so, Mr Bowman said.

Shearers could refuse the extra hours if they deemed them unreasonable.

But there would be no changes to the 40-hour week or pay rates for shearers working for unincorporated wool growers until the Australian Industrial Relations Commission took over from the Australian Fair Pay Commission later this year, he said.

AWU assistant national secretary Ben Swan said the AWU had been in talks with the NFF on the issue.

"Both sides agree we can work it through to a positive solution," he said.

"We are all trying to deal with this, we are all trying to do the right thing by our respective members.

"While we may have conflicting views about the solution, we all believe it will be fixed by the relevant authorities."

But Mr Bowman said the AWU must get the message out to workers who did not understand the details.