The Tories say they will deliver 6,000 more doctors in general practice in England by 2024-25 to increase patient appointments, if they win the election.
They claim they will reach that target through additional doctors working and training in surgeries, international recruitment and better retention.
However, Health Secretary Matt Hancock said a previous Tory pledge to recruit 5,000 GPs by 2020 had not been met.
Labour leader Jeremy Corbyn said: "You can't trust the Tories on the NHS."
He said despite the Conservatives' previous promise of more general practitioners made in 2015, GP numbers have declined.
Labour has said it wants to expand GP training places from 3,500 to 5,000 a year to ease the burden on GPs.
The Conservatives say their plan would see the current tally of 3,538 GPs in training every year rise by about 500 each year over the next four years.
And recruiting more GPs from overseas while improving efforts to retain current staff would lead to a total of 6,000 more doctors than there are now, they claim.
But it is not yet clear how this will be achieved.
In 2015, the then health secretary, Jeremy Hunt, pledged to have 5,000 more GPs working in the NHS in England by 2020.
Speaking on BBC Radio 4's Today programme, Mr Hancock acknowledged GP numbers had in fact decreased since 2015.
He said: "It's true the number of GPs was falling when I became health secretary [in July 2018].
"The numbers are now rising but I want them to go much further."
Previously the Department of Health said one of the challenges it faces in growing GP numbers is a irise in those taking early retirement and part-time working.
Richard Murray, chief executive of health think tank the Kings Fund, said the announcement only goes part of the way to solving this "vicious cycle" of hiring and retention.
"The outflow from General Practice is the problem the government's facing.
"They're not succeeding in retaining, particularly older GPs, and younger GPs wanting to work part-time."
The party has also promised to recruit 6,000 more NHS nurses, physiotherapists and pharmacists to work in surgeries.
And it plans to modernise systems for booking appointments and ensure all patients have the choice of a consultation on the phone, on Skype or online.
With more than 300 million appointments every year in England, the Conservatives forecast 15% more being created as a result of these plans.
The party said it plans to invest £2.5bn in the project over four years in addition to the £20.5bn of extra NHS funding pledged by Prime Minister Boris Johnson.
Dr Richard Vautrey, from the British Medical Association, said: "We wait with some trepidation to see if this latest promise can deliver.
"The lack of detail as to exactly how all these promises will be made good, particularly with no firm commitment for full reform of the ridiculous pension taxation system, means it remains to be seen whether these long overdue and very necessary improvements will be achieved."
Waiting times for a GP appointment have become the national conversation - the words of the chair of the Royal College of GPs.
Doctors say they are working flat out but are struggling to keep up with rising patient demand and filling vacant posts in general practice is increasingly difficult.
So how much difference will the Conservative plans make if they are re-elected? Funding extra training places will result in more doctors going into general practice.
But half the 6,000 additional doctors promised by 2024 are assumed to come from international recruitment and better retention of existing staff, neither of which has been easy in recent years.
Some GPs have retired early because of tax bills associated with their pensions, an issue which has not yet been fully resolved.
Achieving that 6,000 total looks a big ask. As the government discovered, setting a target of 5,000 by 2020 was one thing, but achieving it another matter altogether.
The announcement comes after the party promised to make it easier for doctors and nurses from abroad to work in the UK after Brexit, by creating an NHS visa.
Health Secretary Matt Hancock said the government recognised GPs were under increasing pressure and require funding "to help everyone get the care they need".
He said extra appointments in GP surgeries would be created "with the sort of easy online booking that we expect in other areas of our lives".
Speaking at the Labour party conference, shadow health secretary Jon Ashworth said: "You can't trust the Tories with our NHS.
"They always make election promises which they fail to deliver on.
"Tory ministers promised us 5,000 extra GPs but in fact we have lost 1,600 GPs under the Tories."
Prof Helen Stokes-Lampard, chairwoman of the Royal College of GPs, said GPs were working flat out to try to keep up with rising demand while there was a shortage of doctors and other staff.
She said urgent action was needed to support GPs "grappling with unmanageable workloads", adding that they go above and beyond for patients, often to the detriment of their own health and wellbeing.