FILE PHOTO - Pedestrians walk at a scramble crossing at Shibuya shopping district in Tokyo, Japan September 15, 2017. REUTERS/Toru Hanai/File Photo

TOKYO (Reuters) - Japanese workers’ monthly wages were underestimated by 0.6 percent on average in the 2012-2018 period due to a faulty polling method that came to light recently, government officials said on Thursday.

The results were reported to the government’s statistics panel by the labour ministry which recompiled its wages data following the revelation last week that it miscalculated workers’ average wages for years.

Inaccurate wage data makes it difficult to assess whether Japanese Prime Minister Shinzo Abe’s policies are working and could raise questions about the credibility of other data, leaving policy makers blind-sided in their efforts to foster sustainable economic growth.

The government is set to revise its budget draft for the next fiscal year starting April 1 by adding 650 million yen ($5.96 million) in spending to make up for a shortfall of employment insurance benefits caused by the wages data errors, government sources told Reuters on Thursday.

Abe’s cabinet last month approved a record 101.5 trillion yen ($931.45 billion) annual budget draft, featuring spending to offset the pain of a planned sales tax hike scheduled for October.

Wage data out last week showed nominal cash earnings grew 2.0 percent in the year to November, with monthly pay up 1.6 percent year-on-year.

($1 = 108.9700 yen)