There have been fresh calls for the UK government to put pressure on France over the murder of teacher Carl Davies, which happened more than six years ago.

The body of the former Royal Marine, who worked at Sittingbourne Community College and later at the Isle of Sheppey Academy before joining a security firm tackling piracy, was found on the south Indian Ocean island of Reunion in November 2011.

A petition for the UK to raise the case with the French government has been created following the release of Vincent Madouré, who was found guilty of the 33-year-old’s murder.

He was convicted after a three-day trial in the island’s capital Saint-Denis in June last year, but it later emerged he had been released in October under judicial supervision after his appeal for a retrial was successful.

Carl’s sister, Kerrie Stewart, said: “We just want the British government to do more to support Carl’s case.

“We know it’s not their jurisdiction but there are other ways they can help by maintaining the pressure on the French government.

“It’s not right that Vincent Madouré has been released. He was found guilty unanimously by a jury.”

The 37-year-old said the family believe other men were involved in the crime who they also want to face trial. “He did not act alone,” she said.

“He is not guilty without the rest.”

The family, who were from Harrietsham, now live in Scotland.

After hearing about the 'Justice for Carl Davies' campaign, ex-soldier turned author and entrepreneur Jordan Wylie has decided to take on the family’s case.

Mr Wylie, who has created an online petition, previously helped with the campaign for the release of the Chennai Six – a group of British soldiers held on weapons charges in India since 2013.

No date has been set for Madouré’s retrial and the family were told they could have to wait until next year before they face the prospect of going to Reunion all over again for the hearing.

The petition has so far reached more than 2,000 signatures. If it gets to 10,000 the government will respond and at 100,000 it will be considered for debate in Parliament.

Kerrie called on her brother’s home town to add their names, saying: “There has got to be at least 100,000 people in Sittingbourne who could sign this petition.”

"It's not right that Vincent Madouré has been released...he was found guilty unanimously by a jury" - Kerrie Stewart

Kerrie Stewart welcomed Jordan Wylie who has become an “ambassador” for the campaign.

She said: “He read about our case and he decided to take it on.

“He wanted to be the ambassador to help us secure justice and make sure that these men face trial so they cannot harm another person.”

Mr Wylie said he has been following Carl’s case since it happened and he could not believe the family is still awaiting justice to be served.

He said: “After I finished campaigning for the Chennai Six last year, which was another huge miscarriage of justice which saw six former British soldiers let down by those they protected for so many years, I made a promise to Carl’s family that I would do my very best to bring Carl’s case back into the limelight in their fight for justice.

“I will be campaigning hard and using my extensive personal network to make sure this is on the British government’s and in particular Boris Johnson’s agenda ASAP.”

He added a short awareness film is currently being made about the case with hope of getting 100,000 signatures so it cannot be ignored any more.

“I encourage everyone to sign the new petition,” he said.

“We have a duty to help a man who is no longer with us, who served exemplary for his country in Her Majesty’s Royal Marines.”

• To view the petition, go to petition.parliament.uk/petitions/208723