The Prime Minister has used the resignation of ICAC-mired Senator Arthur Sinodinos to sack gaffe-prone Defence Minister David Johnston and shake up his ministry.

The long-expected departure of the bumbling Johnston — yet another in a long succession of Defence Ministers from both sides for whom Russell Hill has been the end of the line — sees Kevin Andrews moved from Social Security, a portfolio suited to his interests in promoting a conservative family agenda, to Defence, where he has no experience. It may be a signal that Andrews — long incumbent on the “dead wood” list of Abbott’s frontbenchers — is not expected to continue in politics much longer.

Johnston’s mooted replacement in Defence was expected to be current Immigration minister Scott Morrison. Instead, Morrison replaces Andrews at Social Security. While the appointment has been dressed up as a promotion for Morrison, it looks more like a rebuke for his open desire to expand his portfolio, and possibly a peace offering to Julie Bishop, given Johnston was an ally of hers. However, it also ensures that Morrison doesn’t fall victim to the poisoned chalice Defence portfolio.

Stolid Queenslander Peter Dutton, who has failed to make his mark in the Health portfolio and who has been partly to blame for the government’s struggles over its planned Medicare co-payment, has been given Immigration, although Morrison (and Kevin Rudd, via his deal with Papua New Guinea) has already done the hard work of stopping the boats. Dutton’s shift has allowed the Prime Minister to finally appoint a second woman to Cabinet, with current Assistant Education Minister Sussan Ley taking over Health.

Ley has steered the childcare portfolio quietly and effectively while many of her more senior colleagues have bumbled and stumbled, and she was always the best candidate for the next woman into a Cabinet where Julie Bishop was the only female.

Josh Frydenberg will replace Arthur Sinodinos as Assistant Treasurer, taking some strain off Mathias Cormann, who has had to do both his own and Sinodinos’s job while the latter spent the year benched due to his involvement with ICAC hearings in NSW. That will also allow the current budget process to proceed with all hands on deck, unlike the 2014-15 budget, which plunged the government into woes from which it has not yet recovered.

Queensland senator Brett Mason has also been dumped, while new blood in the form of Kelly O’Dwyer, former WA Treasurer Christian Porter and Karen Andrews has been introduced.

The reshuffle removes the problem of Johnston and resolves the lingering difficulty caused by Arthur Sinodinos’s dodgy memory and poor judgment at Australian Water Holdings, and allows the government to start afresh in the crucial Health portfolio with a more positive, competent and articulate minister than Dutton. However, the problem of Joe Hockey remains, and that is a problem of greater ongoing concern for the government than a bumbler like Johnston.

The full list of the new ministry is here.