The parents of missing United Kingdom woman Sarm Heslop, who vanished in the U.S. Virgin Islands five months ago, are pleading for their government to do more to help the stalled investigation.

"Over the past five months we have endured a living hell trying to piece together what may have happened to our daughter," Brenda Street and Peter Heslop wrote in a letter to U.K. Secretary of State Dominic Raab.

U.K. authorities said in April that they were assisting local police, as is the FBI.

US VIRGIN ISLANDS MISSING SARM HESLOP: PARENTS ‘WANT, NEED AND DEMAND’ ANSWERS 5 MONTHS AFTER DISAPPEARANCE

Heslop, 41, was reported missing by her boyfriend, Ryan Bane, 44, around 2:30 a.m. on March 8. Police told him to contact the U.S. Coast Guard if she had fallen off his 47-foot catamaran, the Siren Song. He did so around 11:45 a.m., and Heslop has not been seen since the night before, when she and Bane went to a St. John bar, 420 to Center, near where his catamaran was moored.

Police have said they could not confirm whether Heslop returned to the boat after being seen leaving the bar with Bane.

Her parents wrote that they believed their government’s involvement in the investigation has been a letdown.

"Disappointingly, we feel that there has been only minimal support from the U.K. government and the Foreign Commonwealth Development Office, and we are now requesting your involvement to do all you can to assist us," they wrote. "Her case deserves a full and thorough investigation, and as the key witness to Sarm’s last known whereabouts, Mr. Bane should speak further with the [U.S. Virgin Islands Police Department]."

RYAN BANE'S ATTORNEY RESPONDS TO USVI POLICE CLAIM THEY ‘LOST TRACK’ OF MISSING SARM HESLOP'S BOYFRIEND

Through his attorney, Bane has said he is "devastated" and "heartbroken" by Heslop’s disappearance and that he had nothing to do with it.

Last month, Heslop’s parents called on Bane to allow police to perform a forensic search on his yacht, the Siren Song, but he is not required to submit to one without a warrant.

US VIRGIN ISLANDS MISSING SARM HESLOP: ‘NOT NORMAL’ FOR POLICE NOT TO SEARCH BOYFRIEND'S YACHT, EXPERT SAYS

VIPD did not immediately respond to a request for comment.

Two of Heslop’s friends, Kate Vernalils and Vitoria Mogridge-Percy, told the BBC Saturday morning that the lack of progress in the investigation would not deter them from searching for their friend.

"We feel like we’ve hit a brick wall and we need the U.K. government to help us find answers for what has happened to her," they said. "We will not stop looking for Sarm."

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Heslop is described as 5 feet, 8 inches tall, slim, with a colorful tattoo on her left shoulder that shows a seahorse, bird, butterfly and pink flower.

Anyone with information on her whereabouts is asked to contact the U.S. Virgin Islands Police Department or Crime Stoppers USVI at (800) 222-TIPS.

Raab's office confirmed it had received the letter.

"We are assisting the family of a British woman who has been reported missing in the U.S. Virgin Islands and are in contact with the U.S. Virgin Islands Police and the U.S. Coast Guard," a spokesperson told Fox News Sunday.