Rural homes and businesses could be "locked out" of 1Gbps broadband for years, an inquiry by an influential committee of MPs has concluded.
The government had failed to properly fund plans to push ultra-fast broadband to the hardest-to-reach areas, it said.
But the government said: "We do not agree with this report, which contains a number of inaccuracies."
The findings come as another UK lockdown means people are reliant on broadband to work and learn from home.
People in rural areas might have less choice of service providers, "may have to pay more and may reach [1Gbps] broadband late", according to the Public Accounts Committee.
It said the Department for Digital, Culture, Media and Sport (DCMS) had failed to make meaningful progress:
- on policy and legislative changes deemed essential by industry to achieve rapid rollout
- to tackle the barriers faced by operators in maximising 1Gbps connectivity
And it had failed to show it had learned lessons from its superfast rollout programme or retain the people, skills and knowledge critical to its success.
Other issues the PAC highlighted included failures to:
- prioritise consumers in rural areas
- reassure local authorities about additional funding to retain their expert resources
Meg Hillier, who chairs the PAC, said: "With the grim announcement that the country and economy will be locked down for months, the government's premises on digital connectivity are more important than ever.
"But due to a litany of planning and implementation failures at DCMS, those promises are slipping farther and farther out of reach, even worse news for the rural excluded who face years trying to recover with sub-standard internet connectivity."
The DCMS said the rollout of 1Gbps-capable broadband had been stepped up "from one in 10 households in 2019 to one in three households today".
"We expect that half of all households will have access to [1Gbps] speeds by the end of this year," it said.
"And the UK is deploying at a faster build rate than comparable countries.
"This is evidence of the progress we have made to support the private sector and reduce barriers to rollout.
"We will take further rapid steps this year alongside the investment being made as part of our record £5bn UK Gigabit Programme, which will focus on ensuring the hardest to reach 20% of the country is not left behind."
Commercial rollouts are expected to provide only 80% of homes and business with access to ultra-fast broadband, with the cost of providing fibre and cable services to rural areas proving too expensive without government subsidies.
According to Ofcom, there are almost 600,000 homes and businesses without access to a broadband connection higher than 10Mbps.
Offering all homes and businesses in the UK 1Gbps broadband speeds by 2025 was one of the key Conservative manifesto pledges in the run-up to the December 2019 general election.
But the PAC said by November 2020, when it had taken evidence from the DCMS, it had become clear this was unachievable.
The government has since revised its target down to "at least 85%" coverage.
The original budget of £5bn was also revised down to £1.2bn over the next four years, leaving experts and concerned parties scratching their heads over how and when the remaining £3.8bn would be allocated.