Around six in 10 people with long Covid in the UK are likely to have been suffering the symptoms for a year or more, figures suggest.

Some 1.2 million of those with long Covid are estimated to have first tested positive for the virus at least 12 months ago.

This is 61% of everyone likely to have symptoms at the start of this year, according to the Office for National Statistics (ONS).

The figure is up from 57% in December and 46% in September.

The latest estimates are based on self-reported long Covid from a representative sample of people in private households in the UK in the four weeks to January 2.

They show the overall number of people with long Covid has dropped slightly month-on-month, from 2.1 million to 2.0 million.

But a growing proportion of this total is made up by people who have had symptoms for a long period.

While 61% said they first had Covid-19, or suspected they had the virus, at least one year previously, 35% said it was at least two years ago – up from 30% in December and 22% in September.

A report published in December by the House of Lords Economic Affairs Committee said it was “unclear” what impact long Covid might be having on the growing number of economically inactive people in the UK – those not in work or looking for work – and recommended further studies be carried out to understand the impact of long-term sickness on employment levels.

Prevalence of long Covid continues to vary by age and occupation.

An estimated 4.6% of 50 to 69-year-olds are currently likely to be suffering from long Covid, the highest proportion of any age group.

This compares with 1.8% of people aged 17-24 and 1.0% of 12-16 year-olds.

People working in social care reported the highest prevalence of long Covid among employment groups (5.7%), followed by civil servants and local government staff (4.8%).

Levels were lower among occupations such as financial services (2.7%) and hospitality (2.9%).

Long Covid is likely to be adversely affecting the day-to-day activities of 1.5 million people – 77% of those with self-reported long Covid – with 380,000 (19%) saying their ability to undertake day-to-day activities has been “limited a lot”, the ONS found.

Fatigue is the most common symptom (experienced by 71% of those with long Covid), followed by difficulty concentrating (52%), shortness of breath (48%) and muscle ache (47%).

There is no standard measure for long Covid, with the ONS using a definition based on symptoms that have persisted for more than four weeks after a first suspected coronavirus infection, where the symptoms could not be explained by something else.