Amy Winehouse's plans to wed Blake Fielder-Civil have been rocked by a woman who alleges she has been having an affair with the singer's fiance.

The troubled star was preparing to remarry Fielder-Civil in the Caribbean next month - but brunette Sarah Aspin claims the singer's ex-husband promised to wed her months ago.

Aspin maintains she fell in love with Fielder-Civil upon meeting him at the Phoenix Futures drug rehab centre in Sheffield, England in April - four months after he filed for divorce from the Back to Black hitmaker.

Relationships were banned in the program, but the couple managed to sneak away every night - and it wasn't long before Fielder-Civil proposed, according to Aspin.

She tells Britain's News of the World, "We spent all our spare time together. He said he'd found his soulmate, that he loved me, as if he had known me forever.

"One day we were talking about our future, whether we wanted kids, marriage. Then suddenly Blake looked me in the eye and said, 'You are the only person I ever want to be with again - will you marry me?'

"I did double check about Amy. He said they were getting divorced. He admitted they spoke... but said he couldn't be with her, that drugs had ruined them."

The former heroin addict was stunned after reading reports about Winehouse's marriage plans last week - because she insists she's been meeting up with Fielder-Civil for the last five months.

She adds, "He told me, I am in love with you and it is you I want to marry. He said he wasn't remarrying Amy. But now I reckon he's stringing us both along and I'm dumping him. Up until last week we saw each other every two or three days."

Fielder-Civil divorced Winehouse in July on the grounds of her adultery.