Japan's premier on Friday reshuffled his cabinet just four months into the job as he looks to rescue plans to raise the sales tax and dig the country out from under its mountain of debt.

Yoshihiko Noda used a round of ministerial musical chairs to rid himself of two under-fire colleagues whose presence had threatened to scupper his legislative programme and sink plans to hike consumption tax.

He also brought in a political heavyweight to help drive through the unpopular tax rise that analysts of all stripes agree is needed if Japan is to get to grips with its huge debt, which stands at around 200 per cent of GDP.

"I've done the reshuffle to create the best and strongest cabinet lineup so as to steadfastly carry out the social security and tax reforms, which we must face, which we cannot avoid or put off," Noda said at a press conference.

All cabinet ministers present at a morning meeting handed in a letter of resignation but the bulk of them were told they would be staying in their posts.

Five were replaced, chief among them were Defence Minister Yasuo Ichikawa and Consumer Affairs Minister Kenji Yamaoka, both of whom have been censured by the opposition-controlled upper house of parliament.

Chief Cabinet Secretary Osamu Fujimura told a press conference that Katsuya Okada, a former party chief, had been brought in as deputy prime minister, a position that previously did not exist, with responsibility for - among other things - reform of the social security and tax systems.

Okada, 58, is a former foreign minister, an ex-DPJ leader and one-time trade ministry technocrat known for his exhaustive policy knowledge and strait-laced "Mr Clean" image.

His political experience is widely believed to be vital if the administration is to garner the cross-party support it needs for tax reform legislation.

Ichikawa's successor as defence chief is Naoki Tanaka, 71, husband of former foreign minister Makiko Tanaka and son-in-law of late premier Kakuei Tanaka.

The new education minister will be Hirofumi Hirano while the new justice head will be upper house politician Toshio Oga
Jin Matsubara is the new consumer affairs minister.

Heavyweight posts including foreign minister and finance minister were unchanged.

The reshuffle was greeted with a political shrug by the opposition, with Nobuteru Ishihara, secretary general of the Liberal Democratic Party, telling reporters Noda had "only changed some faces to cover up his responsibility for having failed to pick the right person" in the first place.

With his approval ratings having slid since he took office in September, Noda is under pressure to do something to stop the rot if he is to avoid becoming the latest casualty of Japan's revolving door premiership, which saw his last five predecessors survive only a year each.

He needs the help of the opposition to pass a package of tax and social reform bills and see through his unpopular plan to raise consumer tax from five per cent to eight per cent in early 2014 and 10 percent in late 2015.

But petty politicking has looked set to derail the plan, with the opposition using the time-honoured technique of targeting individual ministers in a bid to undermine the premier in the highly factional world of Japanese public life.

Yamaoka was ticked off by the opposition-controlled upper house after giving his support to what some have alleged is a pyramid investment scheme.

Ichikawa, meanwhile, has been a liability from day one, bizarrely playing up his lack of knowledge about defence matters soon after being appointed.

He got himself into more hot water when he described the rape of a 12-year-old girl by three US servicemen in Okinawa as a "sexual orgy incident", particularly angering islanders opposed to the huge US military presence there.

Censures of the two men were passed in December by the upper house, which Noda's DPJ does not control, with opposition lawmakers threatening to boycott future votes if the two retained their posts.

Noda had initially refused to bow to pressure to sack the men, but with the re-opening of parliament just days away, appeared to be running out of options.