Heidi Klum has allegedly confided in friends that her marriage problems began a year ago.

The German supermodel and her British musician spouse Seal have confirmed they are separating after almost seven years of marriage.

They haven't given a reason for the split, although Seal admitted in a recent interview that they did sometimes disagree.

A source has told British magazine Look than things have not been right between the couple for some time.

"They're both devastated. But regardless of how sad they are, there must be a part of them that feel relieved, because Heidi says their marriage hasn't been working for at least a year," the insider claimed. "I think Seal can be difficult and has a lot of mood swings. One minute he's the most fun guy in the world, and the nest he's angry over some little thing. I'm sure Heidi's struggled with that and recently I think it's become harder to deal with."

Following their break-up announcement, gossip website TMZ alleged Seal's bad temper was part of the reason the couple are no longer together.

It's also been suggested his wild partying while on holiday with Heidi and the four children their raise last year caused issues between them.