CANBERRA - Australian Prime Minister Tony Abbott on Monday denied that his end-of-year Cabinet reshuffle was due to a bad polling and what he described as a "ragged" conclusion to 2014.

After recent polls, which indicated Labor had taken a 10-point lead over Abbott's Coalition government, in addition to the continuing fallout over his poorly received federal budget, it was speculated that the prime minister's reshuffle was a sign of desperation.

But Abbott said on Monday that the ministerial changes were nothing more than the natural evolution of his government following its first year in office.

Speaking to the Seven Network on Monday morning, Abbott said the rejig was "a good way to end the year after a year of considerable achievement."

The most significant change to Abbott's front bench sees former immigration minister, Scott Morrison, take over the social services portfolio, which has been expanded to include childcare and paid parental leave.

Abbott said Morrison's success in "stopping the boats"and quelling the arrival of illegal immigrants was the main factor behind his upgrade.

"He is a very tough and competent political operator, but he's also an extremely decent human being," Abbott said on Monday.

"He knows what it's like to struggle with a mortgage. He knows what it's like to be looking for childcare, for schools, for health services and all the rest of it."

"What we need is the right blend in these areas, we need good judgment in these areas and that's exactly what you'll get from Scott Morrison."

In his first day as Australia's new social services minister, Morrison put forward his main ambition in the role -- to get the unemployed into a job as soon as possible.

"The best social service we can afford any Australian to help them deal with the costs of living is a job," Morrison said in a statement on Monday.

"Getting as many Australians as are able off welfare and into work will be one of my core goals."

In an effort to "reset and refocus" his front bench ahead of 2015, Abbott has also dumped David Johnston as his minister of defence.

The under-pressure Johnston has been scrutinized for comments made regarding the government's ship-building company, made last month, and has been replaced by veteran Coalition member Kevin Andrews.

"He's copped a bit of flak, unfairly," Abbott said of Johnston on Monday. "He's done a fine job."

In other cabinet changes, Peter Dutton has been made immigration minister, while Sussan Ley has been promoted to minister of health, making her just the second female to hold a position in Abbott's government.