Liam Payne has said his son is ''humungous''.

The 23-year-old singer as four-month-old son Bear with his girlfriend Cheryl Tweedy, 34, and is amazed at how quickly the tot has grown.

He said: ''He's just big in general -- he's humongous. I'm going to get a sore back. He's a big boy! He's healthy, he's strong, he likes his bouncer.''

Bear's quick growth is likely inherited from the 'Strip That Down' hitmaker, as he was also shocked by his own ''chubby'' size in a photo his mother sent him of himself as a baby.

He added to People magazine: ''I thought he looked like me, but then I saw a picture my mum sent me of myself when I was a baby and I was like, 'Woah,' I was a chubster baby.''

Meanwhile, despite the One Direction hunk and his partner - who was formerly a member of girl group Girls Aloud - having an estimated personal fortune of £70 million, the pair have agreed not to spoil their son as they want him to understand the importance of hard work.

Liam said recently: ''We are very lucky and we will raise him to know we've worked hard to have these nice things.''

The singer loves seeing how his son is changing every day and thinks being a father is ''incredible''.

He added: ''I discover him every day and I see his eyes brighten when I talk to him. He always looks at me with great attention and he often tries to imitate me by moving his mouth.

''I'm happy to be a dad, it's an incredible thing. I give my son as much love as I have received from my parents.''

And Liam thinks Cheryl is a ''great'' mother to their tot.

He said: ''I also have an incredible girlfriend, she's a great mum and I could not have been happier to have her as the mother of my child.''