Justin Timberlake defends Britney Spears over her criticised dancing

Justin slammed a number of unflattering Internet videos comparing early performances by Britney with current ones.

The 30-year-old said: 'What a f***ed-up thing to do.

'People think they can say anything and it doesn't matter to people. I'd love to see the people who comment about Britney online say those things to her face, because they couldn't.'

The Social Network star added: 'Also, in Britney's defense, if you pulled up a video I did from 2003, I couldn't do the s*** I did then either.'

Justin added that he's been enjoying pop superstar Lady Gaga - who joined him on the series finale of Saturday Night Live last month.

The Bad Teacher actor said: 'Let's talk about Lady Gaga for a minute.

'She's a force. Beyond awesome... If I were Lady Gaga, I'd do whatever I wanted, which it looks like she's doing. She is just plain old good.'

The former boy band star also spoke highly of teen heartthrob Justin Bieber, but warned him to keep his eyes on the future.

Timberlake said: 'He is obviously a talented kid.

'I just hope he has a good support system, because I think back on myself wearing the cornrows. It's awkward growing up in front of the public.'

The star added to Playboy magazine: '[Justin's mentor Usher] will teach him that you can't just ride this out. You need to have somewhere to go. You need to have a plan, and somebody like Justin Bieber should be thinking about that right now.

'Otherwise, before you know it, there's going to be some kid who's younger than you.'