DNA evidence linking two migrant workers to the murder of two British backpackers, one who was a student at University of Essex, on a beach in Thailand can be retested, it has been claimed.

The defence team for Burmese migrants Zaw Lin and Win Zaw Htun, who are on trial for murder, say Thai police analysis of the DNA is the only evidence linking them to the crime.

The bodies of David Miller, 24, from Jersey, and University of Essex student Hannah Witheridge, 23, of Great Yarmouth in Norfolk, were found on September 15 last year, on the shore of Koh Tao.

Post-mortem examinations showed both had suffered severe head wounds and Ms Witheridge had been raped.

Police had last week claimed DNA samples had been exhausted and could not be retested.

But defence lawyer Nakorn Chompuchat said a forensic expert had testified in court that duplicates of some evidence, including blood-stained sand, had been made.

He said this meant there was enough DNA to be retested.

Mr Chompuchat said the court had asked the defence to submit a request, detailing which samples they would like to be retested.

The two suspects were arrested in early October after police carried out DNA tests on more than 200 people on the island, under intense pressure to catch the murderers.

The men, both 22, retracted initial confessions, saying they were extracted through beatings and threats, which police deny.

Investigators have faced fierce criticism for their handling of the case, including for failing to secure the crime scene and for releasing details of suspects who turned out to be innocent.