Blossoming romance ... Katy Perry and John Mayer - The Sun

KATY Perry steps out to a house party with new boyfriend John Mayer.

The pop star was seen looking cute and girlie in a red floral dress and flat balck ballet pumps as she carried her huge red cork-heeled platforms in her hand.

John channelled his inner-cowboy in a crisp white shirt and jeans teamed with a large fedora hat.

The new couple headed to the private party in the affluent Hollywood area of Los Feliz, before leaving together in John's car.

Earlier in the day Katy, 27, was pictured having a fun day out with friends at a water park, where a wardrobe mulfunction left her showing off a little bit more of her gorgeous figure than she planned on.

Her evening out was the latest in a string of recent dates for the musical duo, as Katy moves on from her failed marriage with British funnyman Russell Brand.

Meanwhile Katy's ex-husband has found love with former talent agent Isabella Brewster.

The 23-year-old American met Russell when they took a yoga class together and their relationship blossomed.

Sources have said that Russell, 37, and Isabella are set to move in together and have been looking at luxury pads in LA.

Last week the couple were seen on a date in London as Russell showed Isabella around his hometown.

Katy and Russell separated in March after just 14 months of marriage.