One Nation Senator Malcolm Roberts has been criticised for charging $20 to attend a cost-of-living summit in Brisbane on Friday.

The federal senator's event has been derided by the Queensland Council of Unions, which accused his party of being "out of touch".

One Nation Senator Malcolm Roberts is hosting a cost-of-living event in Brisbane with a $20 fee. Credit:Alex Ellinghausen

But a spokesman for the senator defended the summit, saying the fee would not cover costs and slamming the unions.

Senator Roberts will be fresh from the High Court in Canberra, where he is one of seven federal politicians fighting a dual citizenship case, to host the Pauline Hanson's One Nation Cost of Living Summit at Queensland Parliament.