Ipswich Hospital has seen the joint-worst decline in the quality of stroke care in the UK, according to a national report.
Data from Sentinel Stroke National Audit Programme's October to December reports show the hospital dropped from an 'A' rating in 2019 to a 'D' rating in 2021.
The only other hospital to see such a decline was Royal Preston.
Health bosses say this "reflects the challenges presented by Covid-19".
A leading stroke charity said nationally the pressures were "enormous", highlighting ambulance delays, stroke staff vacancies, discharge and social care issues.
The Audit Programme says the data results demonstrate the quality of care patients receive across the entire inpatient care pathway, with the rating broken down into 10 domains covering the key aspects of the process of stroke care.
At Ipswich Hospital, the domain which saw the most significant drop was the stroke unit's speech and language therapy, witnessing a fall from a 'B' rating to an 'E' rating, the lowest classification possible.
Dr Angela Tillett, chief medical officer at East Suffolk and North Essex NHS Foundation Trust, said: "We are committed to giving high quality, fast and effective care to stroke patients.
"The most recent SSNAP data for Ipswich Hospital reflects the challenges presented by Covid-19 at the end of last year and the impact it had on patient flow, staffing and staff sickness levels.
"We are working hard on making improvements based on the feedback received."
In the same timeframe, Colchester Hospital saw a drop from an 'A' rating to a 'B' rating and James Paget Hospital dropped from a 'B' to a 'C'.
West Suffolk Hospital maintained its 'A' rating.
Charlotte Nicholls, head of policy at the Stroke Association charity, said: "It's alarming that stroke unit ratings have been deteriorating since the start of the pandemic. We know that staff in stroke units across the country are working incredibly hard to deliver the best care to stroke patients.
"Yet the reality is that enormous pressures on the whole health system - including ambulance delays, stroke staff vacancies, discharge and social care issues - are driving down the quality of some aspects of basic stroke care."
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