Outgoing Council of Trade Union's President Helen Kelly is seeking government approval to use cannabis oil.

Ms Kelly has terminal lung cancer and on TV3's The Nation said she's used cannabis oil before.

She says she didn't like accessing it illegally, so this time she'll be seeking Peter Dunne's permission.

Ms Kelly says she's exhausted all other normal medicines.

An application to use medicinal cannabis oil by Nelson teenager the late Alex Renton was approved earlier this year.