Shadow Health Secretary Jon Ashworth called in at Wood Road Surgery in Wolverhampton – saved after Tettenhall Medical Practice withdrew its request to close it – during a trip to the Black Country.
He joined Eleanor Smith, parliamentary candidate for Wolverhampton South West, who backed the protest, on the campaign trail.
The surgery had been scheduled to close due to rising overheads and GP shortages.
WATCH: Jon Ashworth in Wolverhampton
Local patients won a bitter-sweet victory last week when it was announced the practice would stay open but with reduced hours.
Mr Ashworth said: "The way NHS bosses were trying to jack up the rent meant there was a real possibility that this surgery would close, meaning that local patients would have to travel some distance to see an GP.
"Our Labour candidate joined in the campaign, and I'm here because Eleanor is a real fighter for the NHS and this general election campaign is about the future of the NHS.
"It's about who's going to get the investment for our local hospitals in Wolverhampton, about who's going to end the privatisation of NHS services, and it's about who's going to build an NHS service with extra doctors and nurses for the future.
"I believe that will be a Labour government, with Eleanor Smith part of that government fighting for the NHS and for the people here in Wolverhampton."
Asked about how the party would pay for the extra staff, Mr Ashworth revealed that Labour would be announcing a "proper rescue package" for the NHS in the coming days.
"We've had a decade of cutbacks, of bed losses – we've lost over 15,000 beds in the NHS since the Tories have been in government. We're short of thousands of doctors, and of 40,000 nurses," he said.
"The Tories promised 5,000 more GPs, they've actually cut 1,600 GPs. We've said we will expand GP training places to 5,000 a year, that will mean 27 million extra GP appointments.
"Labour will be investing more in the NHS, and many of these policies are ideas that Eleanor has worked on because she is a former nurse and someone who really is an expert on health policy.
"The rescue plan that we'll be announcing in the coming days will make a real difference to patients in Wolverhampton."
Eleanor Smith said that despite a reduced service, saving Wood Road Surgery was an important victory.
She added: "One thing I've always believed is that once something's gone, it doesn't return. Okay, the hours have been cut to 9am till 5pm but there's the chance, once we get in government, to increase the number of GPS and extend the opening hours here, that's the idea."
Mr Ashworth, who visited Telford's Princess Royal Hospital earlier in the day, went on to Walsall to meet a medical student to discuss training issues and the experiences of junior doctors.