A cocker spaniel died after swallowing toxic algae while swimming in the Lake District, its owner has claimed.
Holly, who was 15 months old, collapsed and started foaming at the mouth just half an hour after taking a dip in Lake Windermere.
Her owner Mark Taras is now calling for more warning signs to be placed around the area to prevent 'another needless death'.
Tragedy: Mark Taras, wife Jackie and eight-month-old daughter Sophie are devastated at the losing pet Holly, who died after eating toxic algae
Collapsed: Holly, who was 15 months old, started foaming at the mouth just half an hour after taking a dip in Lake Windermere
He said: 'I am shocked there were no signs anywhere warning us about it.
'We came here instead of going abroad because we did not want to put our dog into kennels and now we are distraught.
'People come on holiday here with their pets and children and they go into the lake.
'I think that if there is a risk of coming into contact with blue-green algae people should be warned about it. To watch a dog die of it is horrendous. It's the worse thing I've ever seen.'
Mr Taras, from Leeds, had been on holiday in the Lake District with wife Jackie and eight-month-old daughter Sophie.
He said Holly had gone for a swim in Windermere by the couple's caravan on Saturday, but half-an-hour later started foaming at the mouth and then died.
Popular: Lake Windermere is one of the biggest attractions in the Lake District
The couple took their pet to Oakhill Veterinary Group, in Windermere, where they say a vet told them their dog had died from swallowing the toxic substance.
WHAT IS TOXIC BLUE-GREEN ALGAE:
Mr Taras said that after complaining to the Environment Agency, the authority had put up temporary signs close to where Holly had been paddling.
But he added: 'The signs are flimsy and have probably been put there to pacify us because we complained so much, but there should be proper signs.'
The family has now produced a leaflet and intends to visit surrounding areas to inform dog owners of the potential risk.
Graham Miller, environment management team leader for the Environment Agency, said: 'We have taken two recent samples from Windermere at the west shore to test for blue-green algae.
'This was in response to a report from the public of a possible blue-green algae bloom. Both of these samples were clear.'
The vet was not able to comment due to client confidentiality.
Last June two other dogs died after swimming in the lake - a four-year-old greyhound called Jem and a lurcher.
Jem's owner, John Pratt, said: 'He just collapsed. One minute he was fine and the next he couldn't stand.'
And last September the UK's biggest swimming competition, the Great North Swim, was cancelled due to the prevalence of blue-green algae in Windermere.
Poisonous: Blue-green algae can cause stomach upset or rash in humans