Former X Factor judge Tulisa Contostavlos was arrested today on suspicion of supplying class A drugs, sources said.

The 24-year-old singer, who found fame with N-Dubz, was arrested along with a 35-year-old man by appointment at a central London police station and they both remain in custody.

Her arrest came as X Factor judges Nicole Scherzinger, Gary Barlow, Louis Walsh and Sharon Osbourne arrived in Glasgow for the first of this year's auditions.

Metropolitan Police had said its officers were ''considering'' information after a newspaper suggested Contostavlos had acted as a go-between in a drug deal by introducing a journalist to an alleged supplier.

The Sun On Sunday reported that half an ounce of cocaine changed hands as a result of the deal conducted at London's Dorchester Hotel.

A Met Police spokesman said today: "Officers from Westminster have today, Tuesday June 4, arrested two people - a 35 year-old man and a 24-year-old woman - by appointment at a central London police station on suspicion of being concerned win the supply of class A drugs.

"They remain in custody at a central London police station."

Contostavlos' spokesman declined to comment on the development.

Contostavlos was officially dropped as a judge on The X Factor just days ago, with Sharon Osbourne returning to the show in her place.

The star - whose debut solo album made it to only number 35 in the charts - won an apology last year from a former boyfriend who leaked footage on to the internet of the two of them performing a sex act.

When asked about taking over from Contostavlos on the X Factor during the Glasgow auditions, Osbourne said: "Nobody could replace anyone. It was just great to come back for the 10th anniversary."

In reference to Scherzinger, Osbourne said: "I love her. I've known her for a long time, she's fantastic."

Barlow was tight-lipped about the show and declined to comment, but Walsh could not hide his enthusiasm. He said: "I'm happy, I'm nervous and I'm looking for stars."

Meanwhile Scherzinger appears to be settling into British life with ease, choosing to talk about the weather as she arrived.

"I love it here. It's such a gorgeous day. Is the sun always shining or did I just bring it?" she quipped.

"I'm looking for great talent. I'm just looking to be of service to you."

She also said she is excited to be working with Osbourne.