Natasha Hamilton has accused an unnamed man of rubbing his penis against her on a train.

The 36-year-old pop star has detailed the incident on her Twitter account, accusing the ''vile man'' of deliberately pressing himself up against her on a London train and Natasha has since reported him to British Transport Police.

She wrote on the micro-blogging website: ''This vile excuse of a man just had his penis pushed up against me while on the overground train from London Bridge heading to Elmstead Woods.

''Honesty I am shaking a feel so violated now! But more than anything I am so angry!! I had the opportunity to take his picture before he left the train - this has to stop happening to people! (sic)''

Meanwhile, the former Atomic Kitten star previously hit out at people who labelled her a so-called four-by-four mother.

Natasha - who has kids Josh, 16, Harry, 13, Alfie, eight, and Ella, four, by four different men - insisted she doesn't have any regrets, despite what her critics say.

She explained: ''I do get people saying nasty things because my children have different dads. But I feel I would have been a worse mum staying in relationships that were detrimental to me and my children's happiness.''

The pop star also revealed that her oldest children were more understanding of the situation.

Speaking in 2015, she said: ''Josh said to me recently, 'Mum, I really admire what you've done in your life because you're not willing to settle for anything other than the best.'

''I was so touched. They're wonderful kids and hopefully I can pass on some wisdom, so they make good decisions.''