LONDON, March 20 (Reuters) - Britain should keep competition in fast broadband to drive full-fibre coverage to 96% of premises by 2027, while capping the price BT's Openreach can charge for slower speeds up to 80Mbit/s, up from 40Mbits/s today, Ofcom said on Thursday.

Four years ago, the regulator encouraged companies to build gigabit-capable networks by promoting competition and by making it easier for new entrants to use ducts and telegraph poles owned by Openreach, the national network provider.

The measures helped drive the roll-out of full fibre networks from less than a quarter of premises to nearly seven in 10, Ofcom said.

It proposed keeping the price of high-speed products free from regulation for five years from 2026, while protecting consumers using copper-fibre connections of up to 80Mbit/s by capping the price Openreach can charge to retail providers such as Sky and TalkTalk.

In the most remote parts of the country where new commercial networks were less viable, it said it would promote investment by Openreach.

Openreach said it was vital that Ofcom delivered the certainty and stability it needed to continue investing.

"At first glance, these proposals offer broad continuity, but we'll be engaging closely with Ofcom on the details," said its regulation director Mark Shurmer.

Shares in BT rose 1.3% in morning deals.

Ofcom's previous regime helped trigger a wave of investment from new players, known collectively as altnets.

Leading altnet CityFibre, which has signed Sky to its network, said Ofcom's support for wholesale network competition had driven better services, greater choice and lower prices.

"We fully support Ofcom's direction and look forward to working together to ensure the UK benefits from a thriving, sustainable digital infrastructure market," said chief executive Greg Mesch.

Ofcom will consult on its proposals until June 12 before making a final decision next March.

(Reporting by Paul Sandle; editing by Sarah Young and Louise Heavens)