Green campaigners urged David Cameron yesterday to stop trying to appease a minority of windfarm opponents in his party with proposals for further curbs on onshore turbines.

Supporters of wind power were alarmed after it emerged that the prime minister was considering including new controls on onshore generation in the next election manifesto, such as a cap, further cuts to subsidies, more planning restrictions or limits on noise from turbines.

A Conservative source indicated that Cameron is "of one mind" with some of the loudest opponents of onshore windfarms and wants to go further in cutting government support for them.

Critics accused the prime minister of pandering to the right of his party before the election, as there remain many Tory backbenchers who dislike onshore windfarms and Ukip has declared its opposition to windfarms on principle.

Although the coalition has already set out cuts to financial support for windfarms and given communities greater rights to veto developments, Downing Street plans for further controls are already under way. It is understood that Cameron and George Osborne proposed a cap on the electricity output of onshore windfarms to Nick Clegg just over a week ago, meaning no more would be built beyond existing ones and those already granted permission. This was rejected by the Lib Dems but could form part of a Conservative pledge in the runup to the next general election.

Chief executive of the European Wind Energy Association, Thomas Becker, said he feared the political confusion over onshore wind was creating a "vicious" climate for investment.

"In our opinion, leaders in Europe, including in the UK, need to make up their mind whether they would like wind infrastructure. We're not selling washing powder. We're establishing things that last for 20, 30, 40 years. That's a huge investment and the political insecurity that [comments] like this creates is very vicious to our industry, in that investors and developers shy away.

"There is a tendency in which energy policy is being treated by the political levels as something you can turn off and on every election. "Investor insecurity, the constant political changes, create scepticism with investors, which makes energy more expensive … I can tell you that, not least in the City of London, investors are upset about what is going on. I am in daily contact with them and it is certainly not good what is happening at the moment."

The deputy chief executive of industry lobby group RenewableUK, Maf Smith, said the row risked harming investment across the energy sector. "Onshore wind is the cheapest mainstream renewable technology, and will be cheaper than new nuclear," he said. "Rumours like this make the UK look a less secure place to invest."

Alasdair Cameron, a renewable energy campaigner at Friends of the Earth, also expressed disappointment at political rhetoric against a "cheap and popular way of generating clean energy".

He said: "Instead of trying to appease a minority of his party, Cameron should be formulating a national energy policy that balances security, cost and decarbonisation. For onshore wind, that means improving planning processes and increasing community involvement to help spur more and better developments."

Tim Yeo, the Conservative chairman of the energy select committee, was more philosophical about the potential changes, saying a cap on onshore wind output would probably not make much difference given that many projects are already choked off by the planning system. He also said investors in windfarms should expect lower subsidies in future years as the technology becomes cheaper and more economically viable with less taxpayer support.

He said: "By far the biggest obstacle for onshore wind is planning. That is something that has deterred a lot of people already. Whether we have a cap as well or not, I think is largely academic."

Nevertheless, senior Liberal Democrat sources said the proposal of a cap meant Tory claims to be green were "already a lame duck and are now dead in the water". Clegg told Cameron he was free to put the idea of greater curbs on windfarms in the next Conservative manifesto but it would absolutely not be sanctioned under the coalition, the source said.

The source added: "Nick Clegg was simply not going to allow the Tories to move the goalposts on green energy again. Some sort of crude block towards onshore wind would seriously damage investor confidence in Britain's energy markets. It would be a double whammy – bad for British business and for the environment.

"The Liberal Democrats believe in a mixed, diverse green energy future. Capping onshore wind production would leave investors questioning our long-term commitment to all renewable energy sources. This would be catastrophic for our growing green economy and the hundreds of thousands of British jobs in it."

There are more than 4,000 onshore wind turbines generating almost 5% of all of electricity, and 3,000 more have planning approval. As well as restricting any more turbines beyond these, the senior Tory source said other options were further cuts to subsidies aimed at making it more economically difficult for current windfarms to operate and extra controls on planning permission.

In public, the government claims it supports onshore wind energy as long as communities have more power of veto over unwanted developments. Asked on Tuesday about whether Cameron proposed a cap on onshore output when meeting Clegg, the prime minister's spokesman refused to answer the question four times.

He told reporters: "[Cameron and Clegg] meet very regularly and I don't go into the details of what they discuss. We want local communities to have a greater say in the planning decisions with regards to onshore windfarms, and changes were made in recent months to strengthen local communities' involvement in those decisions."

The latest row comes months after the government agreed that subsidies for onshore turbines would be cut by 5% a year after 2015 under a deal reached by the coalition partners. In 2012, support for onshore wind was cut by 10% after the prime minister came under pressure from more than 100 backbench MPs, who wrote to him demanding action against windfarms spoiling the landscape in rural areas.

The government also announced extra planning restrictions, with the communities secretary, Eric Pickles, promising to give local communities a greater say on where windfarms were built. Surveys consistently show public support for windfarms and green energy, even among Tory and Ukip voters.

But Cameron remains under pressure from backbenchers to reduce support for onshore windfarms over planning concerns and the level of subsidies on household bills. In November, the Sun and the Daily Mail said he ordered aides to "get rid of all the green crap" from energy bills to bring down costs. According to the reports, Cameron used the direct language to dismiss green levies, which go towards paying for renewables and helping poor people cut energy use. At the time, No 10 denied the report, saying it did not recognise the language. However, officials did not appear to deny the sentiment, pointing out that the PM has repeatedly promised to roll back green taxes.

The coalition has now scrapped environmental levies amounting to £50 a year per household if the cuts are passed on by energy companies. There are fears within the green industry that the government will come under further pressure to cut environmental levies to pay for energy efficiency and low-carbon power.