Rates on loans between £5,000 and £7,499 have been cut to 4.5% APR while loans over £15,000 are now available at 4% APR.
The rates will be available until Wednesday 30th September 2015.
Steve Fletcher, director of retail banking at the banks, said: “We recognise that there are different times when people need to take a loan and Clydesdale and Yorkshire Banks are focused on offering competitive rates for both new and existing customers however they apply.
“We hope that by offering our lowest ever rates we can help make it easier for customers especially those considering larger purchases such as a car with fixed monthly payments over a set period of time.”