Nickelback singer's ex claims he cheated on her

Avril Lavigne is engaged to Nickelback singer Chad Kroeger. Photo / Supplied

Avril Lavigne's fiancé Chad Kroeger reportedly cheated on his girlfriend to be with the singer.

Kristen DeWitt from Salem, Ohio said she had been quietly dating the 37-year-old Nickelback rocker for years after his break-up from long-time girlfriend Marianne Goriuk in 2002.

However things took a turn for the worst about four months ago according to his 27-year-old former partner.

"Chad and Kristen were happily dating until they made a mutual split in May," a source told website RadarOnline.

"His engagement to Avril completely caught Kristen off guard and the timelines don't match up. Chad had to have been seeing Avril behind Kristen's back."

When the engagement went public on Tuesday Kristen took to Twitter to express her shock saying, "The moment u find out ur ex of four months engaged the girl he was cheating on you with! #classic."

But before news of 27-year-old Avril and Chad's engagement broke, someone tipped her off, asking whether or not she was aware that he may have been seeing someone else.

She replied: "Not to my knowledge, the man barely has time to eat during the day. This is the first I've heard of It n we've remained close."

According to reports, Avril and Chad have been dating for half a year before proposing marriage - which would mean they began seeing each other in February, but he and Kristen didn't break up until May.

Chad admitted in April to 'Dave & Jimmy' from WNCI radio: "Yes I'm dating a girl from Ohio."

-BANG Showbiz!