The estimate comes as NHS leaders in Essex launch a campaign to reduce missed appointments, after collecting data that show around 12,000 are missed each month across five of the county's CCGs.
Information collected by five CCGs across mid and south Essex showed that across 44 practices in Basildon and Brentwood, 450 hours of GP appointment time was wasted per month.
Across 49 GP practices in Mid Essex CCG, 240 appointments were missed in a single day. In Thurrock, 2,900 GP appointments were missed across 35 practices in the month of December 2016, while 500 were missed in a week at the 25 practices in Castle Point and Rochford CCG and further appointments were missed in Southend.
The five CCGs estimate that across their combined patch, 12,000 GP appointments are missed each month because patients fail to attend - equivalent to 3.5% of the total number of appointments available.
GPC deputy chair Dr Richard Vautrey told GPonline that he believes the national DNA rate is higher, at around 5%.
The Essex figure of 3.5% of appointments missed is based on a figure cited by the BMA as the minimum number of appointments required by a standard population - 72 appointments per 1,000 patients per week.
Using this figure, the Essex CCGs calculate that their practices offer 338,112 appointments per month to their combined population of nearly 1.2m patients. The 12,000 missed appointments are equal to 3.5% of total appointments available monthly.
Across England, if 3.5% of appointments are DNAs, this would mean that more than 7m are lost annually. The GPC estimate of 5% would mean more than 10m are missed.
General practice DNAs
Even this figure is well below an estimate of 12m DNAs in general practice cited by NHS England in 2014, or the 14m DNA estimate produced by a GPonline poll of more than 500 GPs in 2015.
Dr Vautrey told GPonline: 'The 3.5% figure sounds a bit low - I would expect that nationally the figure is nearer to 5%. In a typical surgery of 20 patients, expecting one appointment to be missed is not unreasonable.'
He said the scale of the problem with missed appointments varied significantly between areas, but he added: 'The reality is that it is a significant issue. At a time when many patients are struggling to get an appointment, the fact that so many patients forget or don’t go when they have made an appointment means others can’t go. It has a big impact on practices.'
He said DNAs had 'always been a problem' for GP practices and that it was difficult to say whether the issue was better or worse now than in the past.
'It's very difficult - there is no one solution,' Dr Vautrey said. 'Even when there is extremely good access and booking on the day, patients still miss appointments.'
He said practices should have clear policies to tackle the issue, and that many operate systems that mean three missed appointments trigger a warning letter to patients if there is no good reason or attempt to cancel.
Southend CCG chair Dr José Garcia Lobera said: 'As GPs we work hard to meet the needs of our patients and make it as easy as possible for them to see their doctor. But we need patients to do their bit too by letting us know if they need to cancel or rearrange their appointment.
'The knock-on effect of someone missing their appointment is that some patients who cannot see their GP choose to go to A&E instead and this puts pressure on the hospital. Patients should make sure they attend an appointment if they book one or cancel it if they no longer need it, so it can be made available to someone else.
'There are now many ways of cancelling an appointment, via online services, telephone and even by text in some areas.'