UK investment in green energy failed to pick up significantly in 2011, reflecting difficult economic circumstances and uncertainty over government policy. The government's figure of £2.5bn is slightly higher than an estimate for the previous year and well down on total investment in the sector in 2009.

The Department of Energy and Climate Change said the investment, which represents the total financial commitments announced by a variety of companies between April and December to proposed renewable energy projects, had the potential to create 12,000 jobs across Britain.

Chris Huhne, the secretary of state for energy and climate change, said: "Renewable energy is not just helping us increase our energy security and reduce our emissions. It is supporting jobs and growth across the country, and giving traditional industrial heartlands the opportunity to thrive again."

But the £2.5bn investment announced since April showed little progress from 2010, when £2.1bn was poured into renewables and other low-carbon forms of energy in the UK, according to the US-based thinktank Pew Environment Group.

The 2010 figure was itself a dramatic fall of 70% compared with the investment reached in 2009, when at least £7.1bn was put into the sector.

DECC said this year's investment figures were the first it had compiled, so direct comparisons with previous years have not been possible because Pew's methodology was likely to be different. However, the department agreed that Pew's figures could be used as an indication.

Investors have complained of a damaging uncertainty in government policy, as twice this year the government cut the subsidy rates available to solar energy, and this autumn announced plans to reduce the incentives for wind power.

In 2010, the UK fell out of the league of the top 10 countries around the world in terms of renewable energy investment. This year's figures are extremely unlikely to redeem the UK's place in the league, as many countries in the developing world in particular have surged ahead, including China and India.

The fall in investment in renewables confirms research by the Guardian earlier this month that showed the number of wind turbines built this year is down by half on last year. In the year to the end of November, 540MW of new turbines, on land and offshore, were built – comprising 200 onshore turbines and 50 offshore. In 2010 more than double that capacity – 1,192MW of turbines – were constructed.

This contrasts sharply with more than 30GW of gas-fired electricity generation that is in the planning stages. Charles Hendry, minister for energy, said oil and gas were crucial to the UK economy, contributing about 2% of GDP. Granting 46 new licences to explore for oil and gas under the North Sea, he said: "Our innovative licensing system continues to make the UK one of the most attractive places to do business. These continued high levels of interest, and the award today of these licences, gives me yet more reason to be optimistic for a prosperous 2012 for the UK oil and gas sector."

DECC said last year there was a 27% increase in renewable energy consumption from 42.6TWh in 2008 to 54TWh in 2010 – representing 3.3% of total energy consumed. The energy from wind generation increased by 46% from 7 terawatt hours (TWh) in 2008 to 10.2TWh in 2010, and in 2010 achieved 5GW of offshore and onshore wind capacity.

There was also, according to DECC, a threefold increase in the use of biofuels in transport from 1% of total road transport fuel supply in 2007-08 to 3.33% in 2010.

Huhne said: "Our renewable target is less demanding than other EU member states, but the effect is bringing real jobs and investment. I do not want the UK to be left behind by turning our back on the green economy. The agreement to negotiate a global deal secured at [international climate change talks in December in] Durban has reinforced major nations' commitment to cutting carbon. We cannot afford to stand alone while the world wises up."