Ellen Degeneres and Portia De Rossi are planning to renew their wedding vows.

The couple - who tied the knot in August 2008 - are organising a lavish ceremony to celebrate their sixth wedding anniversary in Sydney, Australia.

A source said that the duo ''want to show their commitment to each other'' after the chat show host was forced to deny they were having problems in December.

The insider added to America's OK! magazine: ''There have been a lot of headlines suggesting that their relationship is in trouble. They want to quash them.

''[They] are looking to do something on or around August 16, their sixth wedding anniversary, in Portia's home country of Australia. They want it to be in Sydney because the city has a big gay population, and they want to help spur the acceptance of same-sex marriage.''

The happy couple recently splashed out on installing a $35,000 home spa at their house in Holmby Hills, California.

The couple bought the home for a whopping $40 million in January.