Justin Clarke (31) allowed the 5cm lump to grow on crossbreed Brandy's left cheek for several months.

Yesterday, he appeared at Peterborough Crown Court, where he admitted causing unnecessary cruelty to the family pet.

Prosecuting, Robert Starr told the court that RSPCA officers had visited Clarke's house, in Hinchcliffe, Orton Goldhay, Peterborough, in November last year, where they discovered the dog in a terrible state.

Mr Starr said: "The dog had a visible lump on it's cheek.

"When vets examined the dog, it was discovered that the lump occasionally dripped blood, and there was discharge in the left eye.

"There was also swollen tissue inside the mouth, and putting pressure on the tumour caused the dog to yelp in pain.

"Pain killers were injected, but two days later the dog had to be euthanised."

Clarke, who had owned the dog for several years, had the tumour treated in 2006, but it had reappeared a year later.

But the next time he could not afford to pay vets bills, and said he did not know there were services which could have helped him.

Mitigating, Rebecca Keogh told the court: "There is no doubt he loved and cared for the dog.

"There were no other problems with the dog, and Mr Clarke owns another pet, which is perfectly healthy. Brandy was a much-loved family pet, which got a condition the family could not afford to treat.

"The last time the dog needed an operation, he had to borrow £300 from a friend, and this time he did not think the dog was in any pain."

When Clarke was told by the RSPCA that the dog was in pain, Clarke said: 'I just want what is best for Brandy.'

Chairman of the magistrates Phil Collins sentenced a sobbing Clarke to a conditional discharge for a year.

Mr Collins said: "This is a slightly unusual case. We often get cases where animals have been beaten, but this is a case where a misguided young man let something go on when it shouldn't have.

"It was a horrendous tumour, but he clearly loved his dog."

Along with the discharge, Clarke was ordered to pay £100 costs.