Allen was speaking at the launch of the Harrods sale

The 22-year-old, who launched her own clothing label in May, announced she was pregnant earlier this month.

She told BBC Radio 5 Live she turned down "quite a lot of offers" to come up with outfits for other pregnant women.

"My demographic is generally young girls. I don't think a maternity line is particularly suitable," she said.

The singer was speaking at the launch of the Harrods sale in London.

New album

She arrived at the world-famous department store in a green horse-drawn carriage at 0900 GMT to begin the traditional countdown to the opening.

Taking to the stage in a black sequinned gown, Allen joked to the crowd: "I did come in earlier for a bit of a preview, so there's not much left."

The singer also told the BBC she would release her new album in summer 2008.

"It's got to be finished in the next month and a half," she said. "You have to deliver it [to the record company] about four months before it's released."