The Joseph And The Amazing Technicolor Dreamcoat star proposed at their home in Kent last week.
'They haven't set a date yet, but it will probably be later this year,' her spokesman confirms.
To celebrate, Lee, 27, and Denise, 34, have jetted to the Caribbean island of St Lucia for a romantic holiday.
The couple, who met on BBC One talent show Any Dream Will Do, have been dating for 18 months.
Denise was previously engaged to Jamiroquai singer Jay Kay, 39, but they split in 2001.
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