Two in five of eligible people have not been screened for bowel cancer in St Helens – leaving thousands missing out on the potentially life-saving check.
Charity Bowel Cancer UK says more needs to be done to encourage people to the test, which helps to catch the deadly disease earlier and when it is more treatable.
Figures from Public Health England show just 60.1% of the 33,647-strong population of 60 to 74 year olds registered with a GP in the St Helens Clinical Commissioning Group area had been screened for bowel cancer in the two-and-a-half years to March 2019.
That was lower than the England average of 60.5%, and meant 13,426 people were not covered.
People aged between 60 and 74 in England are sent a home test for bowel cancer every two years.
Participants send faeces samples off for testing, to look for traces of blood.
Around 2% of people will have an abnormal result, at which point they will be offered a colonoscopy – an examination of the rectum and large intestine – to check for bowel cancer.
Dr Lisa Wilde, director of research and external affairs at Bowel Cancer UK, said: "It is disappointing that uptake for bowel cancer screening still remains low in England.
"Taking part in screening is the best way to diagnose the disease early as it can detect the cancer at an early stage when it is easier to treat.
“Quite simply, taking part in bowel cancer screening could save your life and we would encourage anyone to complete the test when they receive it.”
Coverage of bowel cancer screening has improved across England in recent years, with the proportion of people taking part rising from 57.3% in 2013-14 to 60.5% last year.
The same is true of St Helens, where coverage has risen slightly from 56.9% in 2014-15.
Bowel Cancer UK said it was concerned at the "huge variation" in participation in different parts of the country, something which could in part be put down to differences in demographics.
The CCG with the lowest coverage rate was Bradford City, with just 37.9% of eligible people screened.
At the other end of the scale was Rushcliffe in Nottinghamshire, at 69.7%.
Dr Wilde said: "Some of this can be attributed to groups of people being less likely to take part in screening than others, such as those living in deprived areas.
"It is vital that more is done to reduce this inequality."
She added that the introduction of a new, easier version of the home test was a "game-changer", and had been proven to increase take-up rates.
An NHS spokeswoman said: "The NHS has already introduced a new and more accurate way to test for bowel cancer that will catch 1,500 more cancers a year at an earlier stage and will save thousands of lives."
This will be complemented by other improvements, such as widening screening to include those aged 50 and over, she added.