Homes and businesses will have a legal right to demand high-speed broadband by 2020 under new regulations to help the 1.1 million premises which cannot access decent speeds.

The government confirmed that everyone in the UK will have access to speeds of at least 10 Mbps under a regulatory Universal Service Obligation (USO), rejecting a voluntary proposal from network provider BT to improve speeds.

Under the plan, broadband providers will face a legal requirement to provide high-speed broadband to anyone requesting it, subject to a cost threshold.

Ofcom has said 10Mbps is needed to meet the requirements of an average family.

The government said it believed that only a regulatory USO offered sufficient certainty and the legal enforceability required to ensure high-speed broadband access for the whole of the UK by 2020.

It said it welcomed BT's 'continued investment to deliver broadband to all parts of the UK'.

The Better Broadband for Norfolk campaign has rolled out superfast broadband – a higher standard service with 24 Mbps speeds – to 89% of Norfolk premises, with the aim of reaching 95% by 2020.

Better Broadband to Suffolk, meanwhile, has committed to providing fibre broadband to 97% of Suffolk properties by 2019.

Regulator Ofcom said this month that 4% of UK premises, or around 1.1 million, could not access broadband speeds of at least 10 Mbps. Britain also lags behind most of Europe in providing fibre to the home which guarantees the fastest speeds available.

Culture secretary Karen Bradley said: 'We are grateful to BT for their proposal but have decided that only a regulatory approach will make high-speed broadband a reality for everyone in the UK, regardless of where they live or work.

'This is all part of our work on ensuring that Britain's telecoms infrastructure is fit for the future and will continue to deliver the connectivity that consumers need in the digital age.'

A BT spokesman said: 'We respect the government's decision. BT and Openreach want to get on with the job of making decent broadband available to everyone in the UK so we'll continue to explore the commercial options for bringing faster speeds to those parts of the country which are hardest to reach.

'Alongside this, we'll work closely with government, Ofcom and industry to help deliver the regulatory USO.

'We look forward to receiving more details from the government outlining its approach to defining the regulatory USO, including the proposed funding mechanism.'

Alex Neill, Which? managing director of home products and services, said: 'This decision is welcome news, as consumers around the country simply want to know they will be able to access a broadband service.

'The government must now move quickly to ensure consumers get these promised speeds by 2020 and closely monitor the programme to ensure it can keep pace with changing technology.'

Paul Simon, marketing and communications manager at Suffolk Chamber of Commerce, said: 'The use of a regulatory USO should assist the Government in achieving its aim of a floor of 10Mbps for everyone by 2020.

'However, for our members and the wider Suffolk business community, this is a very modest target. The Government needs to be more ambitious, skip a technological generation and deliver a full-fibre network as soon as possible.'

Nova Fairbank, public affairs manager for Norfolk Chamber, added: 'Norfolk's business community regularly report that our county's digital infrastructure is still not fit for purpose, so many will welcome the ability to have the legal right to demand faster broadband speed by 2020.

'However, 10Mbps should only be seen as the starting point. In today's modern world, where technology develops at an increasing pace, our businesses need the technological infrastructure to continue to evolve in order to allow them to operate efficiently and competitively with the rest of the world.'