A plea to postpone the start of the pre-trial hearings of two Burmese men charged with the murder of two UK tourists in Thailand has been rejected.
The men apparently confessed to the killings earlier this month. Police have denied subsequent reports the pair then withdrew their confessions.
Hannah Witheridge, 23, and 24-year-old David Miller were killed in an attack on the island of Koh Tao last month.
The police investigation into the murders has been widely criticised, with the Foreign Office in London expressing concern.
Three witnesses are due to give pre-trial testimony at the court on the island of Koh Samui on Tuesday.
The two Burmese suspects, identified as "Saw" and "Win", both aged 21, are charged with conspiracy to murder, conspiracy to rape and robbery.
Lawyers representing the pair have argued for the proceedings to be postponed because they say they have been allowed too little time to prepare a defence.
Thai police have been criticised for allegedly not allowing lawyers or translators to be present when the suspects were questioned.
Foreign Office minister Hugo Swire summoned Nadhavathna Krishnamra, the Thai charge d'Affairs to the UK on Monday to express concern over the way the investigation has been handled since the bodies were discovered on a beach on 15 September.
The Burmese government and parliament have also issued statements of concern.
'Fair and transparent'
Post-mortem examinations found Mr Miller, from Jersey, died from drowning and a blow to the head, while Miss Witheridge, from Great Yarmouth, died from head wounds.
In a statement, the Foreign and Commonwealth Office (FCO) said: "Mr Swire stressed that there was a real concern in the UK about how the investigation has been handled by the Thai authorities.
"He said that it was crucial for the investigation to be conducted in a fair and transparent way."
Funeral services for Mr Miller and Ms Witheridge have taken place in recent weeks.
- Small island covering 21 sq km north of Koh Samui and Koh Phangan in Gulf of Thailand
- Population of about 2,100 and visited by between 400,000 and 500,000 travellers per year
- Popular with backpackers and divers
- Quieter and less developed than neighbouring islands which are known for nightlife and beach parties