The government has unveiled a new set of exploration licences in the North Sea in an attempt to increase domestic supplies of oil and gas.

Ministers said the offer round – the 28th in British history – would be an important boost for jobs and tax revenues. But the licensing also comes at a time when the current high level of investment is set to drop dramatically unless new fields are found.

“There continues to be extremely high levels of interest in North Sea oil and gas, which is unsurprising when there could be as many as 20 billion barrels of oil still buried deep within the seabed,” said the energy minister, Michael Fallon. “This new round of drilling for offshore oil and gas will help boost growth, energy security, and jobs in the UK.”

Government statistics suggest the UK oil and gas sector supports around 350,000 jobs, and last year attracted a record £14bn of capital expenditure as well as supplying around half of the UK’s primary energy demand.

The previous round saw a record number of licences awarded, including to 21 new entrants. There are now more than 50 companies working in the North Sea, the government said.

Last year 36 offshore projects, with an associated capital expenditure of more than £9bn, were approved. They provide tax revenues of £6.5bn on production and a further £5bn through the wider supply chain in corporate and payroll taxes.

But critics argue that tax breaks are being given to encourage the development of new oil fields at a time when Britain is trying to ween itself off fossil fuels and develop a low-carbon future.

Later this year there will be even more scrutiny when the government is expected to unveil a new onshore licensing round. That will show how many big oil companies are willing to start fracking for shale deposits.