Bosses of a British ferry company have hit back at Ariana Grande amid a row over travel arrangements for her dogs, declaring the singer should have obtained the proper paperwork for the pooches before trying to board the boat.

Grande's mother Joan was charged with caring for the animals, Toulouse and Sirius, during the cross-channel journey from the French port of Calais to Dover in England, but she was barred from boarding because of a discrepancy with the dogs' documentation.

The Break Free hitmaker's brother Frankie ended up staying behind with the dogs and he later joined the rest of the family in the U.K. after securing a vet's certificate and boarding a later ferry.

Both Grande and Joan lashed out at P&O Ferries in a series of scathing online rants, with the singer writing, "This was unacceptable... It was indeed a terrible experience. no animal/human should be treated that way... ever. Don't (mess) w my puppies," while her mother alleged P&O staff threatened to "murder" the dogs and have her arrested.

P&O bosses have now hit back at Grande, insisting she should have made sure her pets' paperwork was in order before trying to move them across an international border.

A statement released by the company reads, "We completely understand and sympathise with Ms. Grande's frustration, given her attempts to do the right thing. However, the documents she presented were not valid to bring her pets into the U.K... We had to advise that a local vet should be visited to put everything in order... We carry in the region of 40,000 pets a year between Calais and Dover as a matter of routine. However, from time to time we have to decline to carry pets due to irregularities with the documentation stipulated by DEFRA (Britain's Department for Environment, Food & Rural Affairs)."