Japan's government thought it was on to a winner when it hired a popular actress with a tough image to help it persuade reluctant citizens to pay their contributions to the struggling state pension scheme.

Then it found out she hadn't been paying them either.

The case of Makiko Esumi, who starred in the 380 million yen ($3.6 million) poster and television campaign, has embarrassed the government and highlighted the delicate state of a pension system creaking under declining income and rising payouts.

"We're very disappointed," a spokesman for the Social Insurance Agency said Wednesday, adding that the agency was considering its next move, which could include legal action.

The main opposition Democratic Party demanded that Esumi appear in parliament to explain herself.

Esumi's job was to help the government persuade more people to pay into the state's basic pension scheme for citizens aged 20 to 59.

Individuals' contributions to the scheme are some 37 percent short of where they should be, reflecting a growing belief among young people that they are unlikely to get much out of the system so there is little reason to pay in. The position is further complicated by the rising numbers of young Japanese opting for a life of casual job-hopping.

Though officially mandatory, it is up to individuals to make the payments unless they are employed by a company, in which case premiums are deducted by employers. The growing number of opt-outs is a serious problem for the government as increased longevity pushes up the amount of money it needs to meet pension payments while a falling birthrate means there will be fewer people able to pay in.

By 2025, Japan is expected to have one person over 65 for every two of working age, the highest ratio among industrial countries.

The government has already decided to increase its own contributions to the state pension.

But it is struggling to find ways to pay the roughly 2.7 trillion yen this would cost as tax revenue falls and Japan wrestles with the largest fiscal deficit of any industrialized nation.

In the commercials, the 37-year-old Esumi gives the camera one of her trademark hard stares, saying "pay now or cry later."

Her management company issued a statement late Tuesday apologizing for the trouble, and said Wednesday that the actress had since paid up.

But she may still cry later if the case ends up in court.