A sex pest has repeatedly exposed himself and masturbated in front of women on the London Underground. 

British Transport Police (BTP) investigating a series of disturbing sex offences have released a CCTV image of a man they believe may have information that could help them.

In the attacks, a man has exposed himself three times on trains in the Brixton area and once near Golders Green in north London.

On Thursday August 31 at around 6.30am a man exposed himself and masturbated in front of a woman on a Tube train from Brixton, BTP said.

He then left the service at Stockwell but around 20 minutes later he reboarded the service to Brixton. 

The man is said to have exposed himself and masturbated again while standing next to another woman. 

On Tuesday September 5 BTP said a woman boarded the Tube at Brixton at around 6.20am and the same man stood next to her on the platform and masturbated. 

When she challenged him about his behaviour he stopped. 

Then on Sunday September 10 a woman entered Golders Green underground station and was followed by a man, BTP said. 

He then stood next to her on the platform and masturbated towards her. 

Your Local Guardian: Do you recognise this man?Do you recognise this man? (Image: BTP)

Anyone who recognises the man in the CCTV image is asked to contact British Transport Police by texting 61016 or by calling 0800 40 50 40 quoting reference number 457 of 31 August. 

Alternatively, you can call Crimestoppers anonymously on 0800 555 111.