Every day the Gillard government's crabwalk away from a surplus becomes more obvious.

It was on display again in question time yesterday when the Prime Minister danced around the promise without once repeating the commitment. To deflect the attack, she called on the opposition to support the spending cuts outlined in the budget update.

Wayne Swan was more direct when he stood by the forecasts in the update. ''We could not be clearer than that,'' he told Parliament, not being clear about the word ''promise'' at all.

One reason behind the apparent reluctance to recommit in the strong language used previously could be the blow-out in the cost of catering for the flood of asylum seekers. The government is desperate to stop the boat people, hence its decision yesterday to excise the entire Australian mainland from the migration zone.

Labor railed against John Howard's bizarre proposal to excise the Australian mainland by the stroke of a pen. But it was the loud objections of moderate Liberals that persuaded Howard to back off. Now nothing is too tough or radical, as Labor fights on two related fronts.

The opposition ridicules Labor's economic expertise, demands the government produce a surplus but predicts that outcome cannot be achieved this financial year. But if that failure occurs, then the opposition will be the loudest critic. This means Labor is not going to fall at that hurdle.

It was curious then that the government's language on the surplus has changed significantly. From being a promise ''come hell or high water'', it is now described as a plan which is ''on track''. Why the coyness?

A signal may be found in the mining tax - it delivered no revenue in its first three months of operation. The tax takes a part of super profits but mining revenue is down, so no joy for Treasury.

It may be that the revenue predictions are much worse than anyone is letting on.

In that case, it might be impossible to deliver a surplus without cutting into Labor-style programs. And any further cuts could undermine confidence or directly weaken the economy, compounding the problem by generating even lower revenue from company tax.

So long as the government continues to duck and weave when asked about its surplus promise, the curious guessing game will continue.

This gives the opposition an easy shot to claim the government is about to abandon its promise.

Ross Peake is Political Editor

Twitter: rosspeakeCT