AAP

Australian shares have opened flat, as investors remain cautious a day after the market closed at its highest level since 2008.

Property group Mirvac is not ruling out a play for rival Australand despite announcing a 69 per cent fall in profits.

Engineering firm Downer EDI's first half profit has grown by 11 per cent and the company has maintained its expectation of improved underlying profit for the full year.

Treasurer Wayne Swan says speculation the government may put up income tax is "ridiculous and absurd".

A collection of lacklustre earnings reports and in-line economic data have capped US stock gains, with the markets gaining no bump -- or loss -- from President Barack Obama's key policy speech.

The federal government says tighter tax avoidance laws impacting multinational companies will protect more than $1 billion in revenue each year.

The Australian share market closed at its highest level since 2008 as bank stocks soared on a better than expected profit from Commonwealth Bank (CBA).

Shares in Skilled Group are up more than four per cent after the labour contractor reported a double-digit lift in first half net profit.

Engineering giant WorleyParsons has posted a flat first half profit result and tempered its forecasts for the full year.

Oz Minerals' full year profit has fallen by more than 44 per cent but the company remains on track to meet its copper and gold production targets.

Rio Tinto's Gove alumina refinery will stay open, the Northern Territory government has confirmed.Chief Minister Terry Mills said the mining giant had agreed to keep he plant open.

Boral chief Mike Kane says the Australian housing market is too difficult to predict as his company posted a first half net loss of $25.3 million.

Consumer sentiment has surged to its highest level in more than two years, fuelled by low interest rates and improving property and share markets.

The Australian share market has breifly broken through the 5,000 point mark as a better than expected profit by Commonwealth Bank boosts sentiment.

Leighton Holdings has returned to profit and driven down debt after least year's heavy losses, and forecast further growth in the year ahead.

A Labor MP insists there is no chance a revived mining industry campaign about the resources rent tax could claim another prime minister's scalp.

Property group Stockland has suffered a $147.1 million interim net loss and flagged lower earnings for the full year.

Commonwealth Bank's first half net profit is up one per cent to a record $3.66 billion.

One of the construction partners for the $37.4 billion national broadband network is significantly behind with its cable rollout in Western Australia, South Australia and the Northern Ter

 The Dow blue-chip stock index has climbed back above 14,000 to a fresh five-year high as markets await President Barack Obama's State of the Union address.

Labor leader Mark McGowan has backed gay marriage and euthanasia during an online question and answer session.

Mining giant Rio Tinto is expected to post a full year net profit of more than $9 billion, driven by the company's iron ore business.

The Australian dollar has fallen to a fresh three-month low on speculation North Korea had carried out a fresh nuclear test.

The Australian sharemarket finished flat after the All Ordinaries index pushed through the significant 5000 point barrier earlier in the day.

Engineering company Bradken has impressed the market by declaring that last year's economic downturn in resources had bottomed out while posting a solid half year profit.

Qantas Airways says its nine million frequent flyers will be able to use points to redeem flights across the Emirates network from March 31.

Business-focused telco Amcom Telecommunications has delivered a 20 per cent lift in first half profit and flagged a similar result for the full year.

The federal government has no plans to change the design of its mining tax, Prime Minister Julia Gillard says.

The central bank will have to cut the cash rate again at some stage given the chronic low levels of business and consumer confidence, a leading business group says.

Business confidence in January mostly held on to its gains made in December, helped by a rally in the local sharemarket, a private survey says.

Gains by the major banks have pushed the Australian share market toward the 5,000 point level.

 Independent MP Rob Oakeshott feels the Gillard government partly duped him about the design of its mining tax.