Japanese Prime Minister Taro Aso's 2 trillion yen ($20 billion) plan to aid households will not be enough to help the economy, said the former economy minister Hiroko Ota.

"I don't think the assistance will be effective, especially considering its size and the fact that it's a one-off measure," Ota said in an interview in Tokyo on Tuesday.

Ota, who was dropped from the Cabinet in August as part of an unsuccessful effort by then Prime Minister Yasuo Fukuda to shore up his popularity, said she would have considered resigning if she had to implement the policy.