Lauren Conrad's jam-packed schedule is the reason she's not appearing in the reboot of 'The Hills'.

MTV has announced plans to revive the hit reality series, but Lauren will not be making a comeback, with a source telling TMZ that she is simply too busy with her other business ventures to commit to the reboot.

'The Hills: New Beginnings' is scheduled to premiere in 2019, yet Lauren is instead focused on her clothing lines and her own stores.

In fact, her business portfolio is considerably stronger than any of her former co-stars, which had made it easier for her to rebuff MTV's advances.

And contrary to speculation, Lauren's decision reportedly has nothing to do with any lingering animosity between herself and any of the show's other big names.

Earlier this week, meanwhile, it was announced that Kristin Cavallari's reality TV show has been renewed for a second series.

The 31-year-old beauty - who also starred on 'The Hills' - confirmed that her hit E! programme 'Very Cavallari' will return to screens next year for a second instalment - made up of 10 one-hour episodes - after the first season proved a huge success with viewers.

She said: ''I couldn't be happier that 'Very Cavallari' will be returning for season two. I had the best time filming our first season and feel like we are just getting started, so I can't wait to come back for more next year!''

Kristin previously said she wouldn't trade her time on 'The Hills' ''for the world''.

She said: ''It got me to where I am today.''

But she admitted she can't bear to watch old episodes of the show.

She added: ''If I did watch them I would cringe. I think MTV played them a couple summers ago and my husband Jay put them on as a joke to mess with me. It was definitely cringe-worthy.''