A political commentator says he doubts an incorrect email sent by the Council of Trade Unions was a genuine mistake.

The CTU's email sent on Sunday night incorrectly claimed National would remove policies like 10 days sick leave and the Winter Energy Payment.

It has now clarified it meant to say they are things National has opposed in the past.

Commentator Peter Dunne says the CTU economist previously gave advice to Grant Robertson.

He says they'd know what was supported by whom.

"And I think the fact that they can get so much of it so wrong suggests that he's either not done his job, or more likely, it was a deliberate attempt to deceive."

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