United Lincolnshire Hospitals Trust missed the national standard for referring patients within two weeks by 87.5 per cent.
The target for hospitals is set at 93 per cent, however in January 2019 the trust managed to refer just 5.5 per cent of patients.
People are expected to be referred to a specialist within two weeks if they are suspected of having breast cancer.
Health bosses said the drop in standards was due to “staffing issues” and apologised.
ULHT also missed the waiting time target in November and December 2018, as well as the symptomatic two-week target which is set at 93 per cent.
However, the trust did meet the 85 per cent standard for a 62 day diagnosis and treatment for patients with breast cancer.
Simon Hallion, divisional managing director for family health at ULHT, said: “Due to staffing issues earlier this year our two week wait fell below the level that we would expect.
“To make sure patients were seen as quickly as possible, we recruited more staff and held additional clinics, including over weekends.
“Although there was a delay in patients having their first appointment, our actions meant that patients were diagnosed and treated within the required 62 day time frame.
“We apologise for any additional worry this may have caused our patients.
“We are pleased to report that we are now meeting national targets.”