You might have thought that Zac Goldsmith would be content to lie low after he was exposed as a non-dom, or that he would have been gagged by a Conservative apparatchik, but apparently not.

The prospective Tory MP used a lecture in London last night to deliver a stinging attack on the Sun over its recent treatment of Gordon Brown.

He said:

[My] heart went out to Gordon Brown and I was repulsed by the Sun and I thought: my God, I did not want this newspaper to be backing my campaign. It is immoral and unethical and wrong. The Conservative Party by default got caught up by this, which is a shame.

Goldsmith's response is that of any reasonable human being, but as a former editor of the Ecologist he's likely to have thought more deeply about press ethics than most.

One wonders if James Murdoch, who runs the show at Wapping, and who worked hard to turn News International into the UK's first carbon-neutral newspaper publisher, will be disappointed by the criticism from a fellow environmentalist. David Cameron, who said he was "delighted" to win the support of the Sun, is also likely to be troubled by Goldsmith's declaration that he wouldn't want the tabloid's backing.

However, there are both principled and practical reasons for shunning the Sun. Goldsmith's claim that the tabloid's association with the party has led to a fall in Tory support is backed up by the latest opinion polls.

Labour will no doubt hope that Goldsmith continues to make such uncomfortable observations in the run-up to the election. Rumour has it that he has been consciously excluded from Cameron's inner circle in recent months.

Much more of this, and Goldsmith, who had been expected to win a key post if elected, will be talking himself out of a job.

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