David Cameron has conducted a surprise mini-shuffle ahead of the Easter break, bringing a controversial rightwing energy minister into Downing Street.

John Hayes will be replaced at the Department of Energy and Climate Change (DECC) by the business minister Michael Fallon, who will straddle the business department while taking on some of his predecessor's responsibilities. Fallon will allow the energy department to send more consistent messages to businesses about its commitment to low-carbon energy.

Hayes, a leading figure in the rightwing Cornerstone group, will act as a sounding board for the right inside Downing Street, a role previously held by Andrew Mackay and Fallon. He has been appointed a minister of state in the Cabinet Office and will attend the key morning and afternoon strategy meetings in Downing Street, giving Tory backbenchers reassurance that they have an ambassador at Cameron's court. Hayes describes himself as the personification of blue-collar Conservatives, and is strong on traditional family issues.

Cameron sent Hayes to DECC six months ago, urging him to represent the anti-windfarm interests on the right. However, it appeared that mixed messages from the department were alienating potential business investors.

One Liberal Democrat source said: "Number 10 is now in 'sell green energy to investors' mode, and they realised that although John was good at playing to the Daily Mail gallery, he was not what companies like Siemens wanted."

Hayes had some ferocious clashes with the Liberal Democrat energy secretary Ed Davey.

At one point Davey's frustration with his junior minister prompted him to write to Cameron to demand that Hayes be taken off the windfarm portfolio because his prejudices were exposing the department to a very high risk of judicial reviews.Cameron took no action, and there has been no immediate policy clash within the department to prompt his ejection. It is understood that DECC's new permanent secretary Stephen Lovegrove, appointed to boost business investment in green technologies, was unimpressed by signals Hayes sent out.

The appointment of Fallon will increase the profile of low-carbon energy inside the Department for Business, Information and Skills (BIS), which used to run energy. It comes at time when critics claim the government has underplayed the importance of green energy in its industrial strategy.

Fallon, a hard-headed effective minister, has piloted private member's bills on green energy in the past. He will now have to balance the need to meet public concerns about the costs of green energy, and the need for investment. He has a substantial brief, making him one of the most important Tory ministers outside cabinet.

It had been Fallon's move to BIS last September which created a gap for an ambassador of the right in Downing Street.

Hayes has wide contacts across the Tory party, including with the critical 2010 intake. One ministerial ally said: "If there are any plots to unseat Cameron, he will either have started them or know about them before they are hatched."

Cameron's supporters will be looking for any signs that the long-rumoured plot to unseat him has substance, and will be unnerved by a YouGov poll showing Boris Johnson would lift the party's hopes of election. The poll shows that the Tories would get 31% in the polls under Cameron against Labour's 37%.

However, when people were asked to imagine how they would vote if Johnson was the Tory leader, the two biggest parties would be level on 37% each — with the Lib Dems squeezed to 11%.