The number of people taking part in strikes has almost doubled in the past year, according to official figures.
A report from the Office for National Statistics found that the number of workers involved in labour disputes increased from 429,000 in the 12 months to September 2007, to 841,000 in the 12 months to September 2008.
The number of working days lost to stoppages was also up, from 677,000 to nearly 1.2 million, according to the November Labour Market Statistics report.
However, there were only 128 work stoppages in 2007-2008, a drop from 151 during the previous year.
A spokeswoman for public sector union Unison said the statistics proved that unions still retained their bite as well as their bark, despite membership numbers being lower than a decade ago.
"These numbers show the extent of feeling by union members about how their pay was being eroded," she told Personnel Today. "The totals probably received a boost from the two-day strike in July, but with more jobs under threat, these figures shouldn't come as a surprise."
Around 234,000 council workers involved in the July stoppage over the government pay offer of 2.45%.
Rob Don, senior policy adviser at the CBI, said the rising figures were driven by an increase in industrial action by public sector workers.
"In the private sector, union membership has been steadily declining for many years, with the latest figures showing that just 16% of workers choose to be represented by a trade union," he said.