A serial sex predator went on to attack two more women after Kent police failed to take a DNA sample from a key suspect, it's been claimed.

Now two officers are being investigated for alleged gross misconduct by the police watchdog the Independent Police Complaints Commison (IPCC).

It comes after 46-year-old John Williams admitted to 11 counts of sexual assault between November 2010 and August 2 last year.

He also pleaded guilty to an indecent assault and attempted handbag theft in 1991, and asked for 16 further offences to be taken into consideration.

Police had been investigating the offences since November 2010, but in October 2012 he was identified as a suspect after a member of the public recognised him in an e-fit.

But no DNA was taken at the time - and Williams went on to commit two further sex attacks.

Eventually, he was interviewed by police in September last year and a DNA sample was taken which matched him to sexual assaults in 2012.

He was later arrested and charged with offences dating back to 1991.

The two attacks from last year were assaults on a 16-year-old in Tunbury Wood, Walderslade in July last year, and two assaults on a 22-year-old in Singleton Lane in August.

Both victims have been told of the IPCC investigation.

Now two officers have been served gross misconduct notices - a detective chief inspector and a detective constable, advising them their conduct is subject to investigation.

IPCC Commissioner Mary Cunneen said: "The fact that John Williams was identified as a potential suspect in autumn 2012, yet a DNA sample was not taken from him until almost a year later, is concerning.

"The fact that John Williams was identified as a potential suspect in autumn 2012, yet a DNA sample was not taken from him until almost a year later, is concerning" - Mary Cuneen

"During the intervening period he carried out two more attacks on young women.

"It is right that we independently establish what actions were or should have been taken by police from September 2012 onwards and the repercussions these may have had on the investigation into the sexual assaults.

"It takes courage for victims of sexual offences to come forward and report their experience to police, and they must do so with the confidence that their allegations will be dealt with promptly and sensitively to support them through the process.

"As the force became of aware of these concerns in October, we are also examining the delay in referring the matter to the IPCC."

A Kent Police spokesman said: "Kent Police strives to put victims first and is assisting the IPCC with its investigation.

"It would be inappropriate to comment any further at this stage."