Two swans were shot with airguns in Accrington with one dying of its injuries.
While a female swan was left with severe injuries to her neck, a male swan died after the attack on Thursday, December 28.
RSPCA inspector Katherine Newman collected the swans from the canal in Chequers, Clayton-le-Moors, after a passer-by spotted the swans were injured.
She said: “This was clearly a purposeful and callous attack on two swans.
"The male had sadly already died with a puncture wound to his head. The female was mobile but was bleeding from two wounds in her neck.
“An x-ray at the vets revealed a pellet lodged inside the head cavity of the male swan and two in the neck of the female, both on their left side.
"The female is now receiving emergency treatment before she will be transferred to RSPCA Stapeley Grange Wildlife Centre in the hope that if she recovers she can later be released back into the wild.
“I am now appealing for anyone who may have seen anything at around 9am that morning to contact us in strictest confidence on 0300 123 8018.”
There were 4,828 airgun incidents reported to the RSPCA between January 1, 2012 and June 30, 2017.
The Government has pledged to review the regulations of air weapon licensing. The RSPCA has been calling for stricter regulations around owning airguns as well as better education and explanation of the law for those buying an airgun.
Inspector Newman added: “Our 24-hour cruelty hotline receives hundreds of calls every year reporting airgun attacks on animals.
"Last year, we received 890 calls and this year looks set to top that and, worryingly, reach a five-year high.
"Animals can suffer horrendous injuries and often die as a result of airgun attacks and these weapons are potentially extremely dangerous for people as well.”
To report animal cruelty call the 24-hour cruelty line on 0300 1234 999.