LOS ANGELES • DJ and producer Calvin Harris criticised his former girlfriend, pop star Taylor Swift, on Wednesday for making him "look bad" after a celebrity news publication revealed that she had written his latest hit song under a pseudonym.

People magazine, citing Swift's representative, said Swift had written This Is What You Came For, which Harris released as a collaboration with R&B singer Rihanna in April.

The magazine reported that Swift had written the song under the pseudonym Nils Sjoberg while the couple were dating and that Swift became upset after Harris said in an interview that he had never discussed collaborating with his then-girlfriend.

That interview with show host Ryan Seacrest took place the day This Is What You Came For was released. They announced their break-up days later.

"Hurtful to me at this point that her and her team would go so far out of their way to try and make ME look bad at this stage though," Harris wrote on Wednesday in a series of tweets directed at Swift.

"I figure if you're happy in your new relationship, you should focus on that instead of trying to tear your ex bf down for something to do."

He praised her lyric-writing talents and said she had wanted to keep their collaboration secret, hence the pseudonym.

Swift, 26, and Harris, 32, split up last month after dating for more than a year. Swift has recently been photographed with British actor Tom Hiddleston.

Harris also hinted at a longspeculated feud between Swift and pop star Katy Perry, saying: "I know you're off tour and you need someone new to try and bury like Katy ETC but I'm not that guy, sorry. I won't allow it."

Shortly after, Perry posted on Twitter a GIF of Democratic presidential candidate Hillary Clinton giving a shrug followed by a silent laugh. Perry, 31, re-tweeted a comment she made in May last year: "Time, the ultimate truth teller."

REUTERS, AGENCE FRANCE-PRESSE