Japanese firms offered their biggest pay hikes in three decades at this year's negotiations with workers, the country's largest trade union group said Wednesday, a development economists say will help revive anemic consumer demand.

A survey conducted by Rengo, an umbrella trade union group, showed pay hikes first reported by unions at the largest employers in March were now broadening to workers at small and midsized enterprises, or those with unions of 300 or fewer members.

The final survey of 5,272 unions affiliated with Rengo showed an average pay hike of 3.58%, or ¥10,560 per month, the biggest increase since the 3.9% seen in 1993. Among them, small and midsized firms raised wages by 3.23%, also the fastest pace in three decades.