Fair Work Commission general manager Bernadette O'Neill told a Senate committee on Thursday claims were up 70 per cent.

"The increase in unfair dismissal has been unprecedented, so significantly higher than any other period from our records," she said.

She said unfair dismissal claims had been constant over a number of years, meaning the spike could be attributed to unemployment stemming from coronavirus restrictions.

Government industrial relations official Martin Hehir said the crisis had sparked high rates of job losses.

"It's not surprising that we're seeing escalation in things such as unfair dismissal," he said.

The unemployment rate recorded its biggest one-month jump on record, rising to 6.2 per cent from 5.2 in March.

Ms O'Neill said the surge in unfair dismissal claims had prompted the commission to ask the government for increased resources.

Meanwhile, the federal government has lowered the minimum notice period for worker votes on changes to enterprise agreements from seven days to one.

Since the change, there have been 30 applications for changes to pay and conditions with 14 giving less than seven days' notice.

Three have used the minimum one day notice for a vote.

Australian Associated Press