Farewell rainbow cake planned for Bullock

West Australian Labor senator Joe Bullock might have quit politics over his opposition to same-sex marriage, but a gay Perth man thinks he deserves a send-off cake - a giant rainbow farewell cake.

Simon te Brinke created a tongue-in-cheek crowdfunding campaign on Wednesday, aiming to send Mr Bullock the cake, adorned with the words "Farewell Joe! Lots of love from your friends at #MarriageEquality xox".

Mr Bullock cited his party's position in support of marriage equality as a reason for his decision to retire from federal politics on Tuesday, making him the fourth WA Labor MP to quit this year.

"Recognition of same-sex marriage by our government will help to send a clear message to young LGBT people (in particular those in crisis) that being in a same-sex relationship is not wrong," Mr te Brinke said on the Gofundme page.