Two Myanmar men given the death sentence for murdering two British backpackers in Thailand in September 2014 have used their last life line and appealed to a court against the sentence.

Migrant bar workers Zaw Lin and Win Zaw Htun were found guilty of murdering David Miller, 24, and raping and killing Hannah Witheridge, 23, whose bodies were discovered on a beach on the diving resort of Koh Tao in Thailand.

Both the men had raped Witheridge and bludgeoned the pair over the head, a court had heard in December 2015.

Their death sentence was upheld by the Appeal Court in March this year when the pair lost an appeal to have their sentence overturned.

Lin and Htun submitted their final appeal on Monday (21 August).

"The deadline is today so we have to submit it. This is the final chance to appeal," Nakhon Chomphuchat, head of the Myanmar men's defence team, told Reuters.

The conviction of the men in 2015 was mired in controversy as they had claimed that the confessions they made during the questioning – which were later retracted – had been extracted through torture or abuse.

The workers earned some supporters who also claimed that the DNA evidence submitted by the Thai investigators was inadmissible as it had not been collected, tested or analysed as per international standards. They also alleged that questioning of the two men was unlawful as it had been done without the presence of the lawyers of Lin and Htun.

Hannah Witheridge and David Miller
The bodies of murder victims Hannah Witheridge and David Miller were found on a beach on the southern island of Koh Tao in Thailand Facebook

Reuters reported that some migrant rights groups also accused the Thai police of failing to properly seal off the area where the crime took place and of using the two Myanmar workers as scapegoats.

The Thai police denied the accusation. The families of the British tourists were also thought to have spoken in support of the police investigation.

There were huge protests outside Thailand's embassy in Myanmar's capital city, Yangon, which lasted a couple of days following the sentencing of Lin and Htun in December 2015.

Reuters noted that although Lin and Htun were given the death penalty, this mode of punishment has not been carried out in many years in Thailand.

Zaw Lin and Wai Phyo
Zaw Lin (R) and Win Zaw Htun (L) have appealed for the final time against the death penalty REUTERS/Athit Perawongmetha