Figures published by the company show it released untreated sewage into the waterways due to overflows caused by storms 22,821 times in 2019 and 65,083 times the following year.
And over that two-year period, the total number of hours the company allowed effluent to spill out rose from 107,836 to 420,419.
Yorkshire Water said it monitored more than twice as many overflows in 2020 and the average rainfall and the number of storms increased, which means “there is more than likely going to be an increase in the total frequency and duration of spills”.
It comes after the Department for Environment, Food and Rural Affairs (Defra) announced that water companies will soon be legally required to secure “a progressive reduction in the adverse impacts of discharges from storm overflows”.
A Yorkshire Water spokeswoman said: “We are committed to further improving the environmental performance of our wastewater assets and pollution in rivers is not something that we or our customers want.
“We take our environmental responsibilities very seriously and making improvements in river quality is a key priority in our future plans, which includes further efforts to reduce intermittent discharges from combined sewer overflows.
“We are calling on Ofwat to let us invest more in this over the next five years to meet demand from our customers to reduce discharges.”
The company has already promised to invest £137m in monitoring, investigating and reducing storm overflows by 2025.
Conservative MPs were last week whipped to vote down an amendment to the Environment Bill, which would have placed a similar obligation on those companies, but the Government has made a U-turn following a backlash from voters.
Government figures show water companies discharged raw sewage into rivers and coastal waters in England more than 400,000 times in 2020, allowing effluent to pour into the water for a total of 3.1m hours via overflow pipes which are used to relieve the pressure on the sewerage network when it is raining heavily.
United Utilities recorded the most spills (113,940) last year and Yorkshire Water was ranked second with 65,083.
This week, the Lords backed, by a majority of 153, a move to place a new legal duty on water companies to “take all reasonable steps” to prevent sewage discharges.
This will allow the Environment Bill to be sent back to the House of Commons where the Government will table its own amendment.
Environment Secretary George Eustice has admitted that the Government’s proposed change to the Environment Bill will still result in rising household water bills.
Mr Eustice signalled that the water sector would have five years to show progress on the matter, but that bills would have to increase to fund infrastructure improvements.
The Minister said: “We’ve been very clear that we want to see a reduction in these storm overflows over the next five-year period of the water pricing plan.
That will need to be funded and will lead to some increases in water bills to fund that.”