Labour is salivating. Until this week the party hierarchy must have thought the only event that could cost John Key the prime ministership would be a video shot of him in bed with a dead woman or a live man.

But Key should face facts. The National leader has been neatly stung by a political desperado either acting on his own or more likely with the connivance of Key's opponents.

Let's be clear, the desperado is not Key's deputy Bill English. There will be more chatter during the election campaign as National's opponents try to draw a link between him and the publication of emails that ended Don Brash's reign.

But the vexed relationship on show is between Key and English. The National leader clearly has a bit of a complex about his deputy, judging by the story that emerged after two journalistic confidantes, who went with Key on a social spree in the Capital earlier this year, let loose that Key expected English to attempt a coup some day, perhaps to wrestle the prime ministership away (assuming he gets there).

A choice confidence that would have left the journalists in no doubt the relationship between National's top duo is pragmatic at best.

It is Key's loose-lipped talk, coupled with the rather too frank comments that English sometimes makes about him, that would have persuaded his opponents that the deputy would be a rich candidate for entrapment. Who can forget his priceless "I'm a stayer, he's a sprinter. I grind away, John just bounces from one cloud to another"?

The English tape is a goldmine. His comments on Working for Families and Kiwibank have given Labour an opening to spin into proof positive that National has a hidden agenda which will result in cutbacks to the tax credits programme and the sale of Kiwibank if it takes office. Key and English had already helped create perceptions of a hidden agenda.

Key's revealing comment in the Weekend Herald's "Unauthorised Biography", where he admitted election policy was held within a tight circle _ "we just can't afford to have an organisation that leaks" _ played into that. So too, English's rather gormless responses when asked for details of economic policy.

But the more damaging factor is the public perception English has created of a less than unified leadership by suggesting Key _ a "nice man" _ doesn't completely understand Working for Families.

English could not have expected to be bugged. But unwittingly, or otherwise, he has broken a cardinal unwritten rule of politics _ don't provide ammunition to the opposition that can be used to destroy your party.