Memo: John Key. Get on top of policy quickly or you may follow Don Brash into oblivion.

And stop blaming journalists for your verbal gaffes _ they're not employed to be your mind-readers.

If Key's advisers haven't delivered him that robust message after this week's gaffes they either lack political smarts or balls. Or are too busy coasting to victory to realise that their election year war-room should be operating 24/7 if National is to stave off the rearguard action now being conspicuously orchestrated by Helen Clark's deputy Michael Cullen.

Cullen should have been easy prey for National this week. His blatant interference in the Canadian Pension Plan's partial takeover of Auckland Airport stank of political opportunism.

But instead of slapping the Finance Minister down and screwing him into a corner over the unprincipled fashion in which the Government delivered its coup de grace to the Canadians' chances, it was Key who ended up as road kill.

Cullen's announcement that the Government had inserted a new clause into foreign investment rules to ensure that local control was retained for strategic infrastructure assets dropped at 7.30pm Monday.

This left plenty of time for Key to consult National's top people to determine the party's response to the Government's controversial policy shift away from New Zealand's open foreign investment regime.

If ever there was a time for National to break its absurd practice of not rolling out policy before the election campaign, this was it. But on Tuesday, Key floundered.

National was so not in control that it did not even direct a question to Cullen in Parliament that day. Key was not able to give direct answers on what National's policy response would be until the Wednesday, by which time TV3's political editor and other media had been running for 24 hours with Cullen's line that Key was "slippery".

Key's failure to get on top of policy detail was again obvious when he failed to remember during a TVNZ interview that National (under his leadership) had set a 2014 deadline for settling Treaty of Waitangi claims.

Cullen, now seeming more like an ancient stealth bomber that has suddenly come to life, quickly made mincemeat of Key accusing him of "making it up" as he went along.

There is an element of truth in the Deputy PM's analysis.

Key comes from a big-time currency trading environment where making calculations on the fly is a standard requirement. Currency traders are responsible for their own books, but they also have to trade within margins.