Katy Perry and Robert Pattinson's text messages have reportedly "hotted up" in recent weeks.

The two stars were romantically linked last summer, before Katy reunited with her ex-boyfriend John Mayer. Even though things didn't progress it's been claimed they never lost touch, with their friendship stepping up a gear following the end of Katy's relationship with John.

"Rob and Katy have never stopped being in touch - she loves the attention but also thinks he's really sexy and funny," an insider told British magazine Heat. "The texting stepped up in January when things started going bad between Katy and John. Rob's been a real shoulder for her to cry on. Since she's been single, though, the texts have hotted up - she loves drunk-texting him and they're always flirty. He's in Toronto filming and they've even planned for her to make a secret trip to see him."

Katy and John split in February, although they haven't discussed why. It's thought Katy's hectic work schedule might have been part of the reason, as she is preparing for a world tour at the moment.

She isn't thought to be officially dating Robert at the moment, preferring to keep things under the radar.

"They've always kept their hook-ups discreet. They're just friends - with benefits - at the moment," the insider claimed.

Katy and Robert were first linked following the end of his relationship with his Twilight co-star Kristen Stewart, who cheated on him with married film director Rupert Sanders.

Last July, Katy attempted to play down the rumours and claimed she'd been in touch with her friend Kristen to discuss them.

“I sent [Kristen] a text message saying, ‘I know you've seen all this stuff but you know I would never disrespect you. I'm not that person. I'm just trying to be a friend to him but it is unfortunate that I do have a set of t*ts,’” she explained to British magazine Elle.