Conservative MP Chris Heaton-Harris is recorded by an undercover investigator for Greenpeace apparently supporting the campaign of anti-wind farm campaigner Greenpeace

The Conservative MP running the party's byelection bid in Corby has been secretly filmed apparently supporting the campaign of a rival candidate.

Chris Heaton-Harris, who is campaign manager for the Tories in Corby, was recorded saying he encouraged an anti-wind farm candidate to join the election race against the Tories, adding: "Please don't tell anybody ever."

The footage, covertly recorded by the environmental group Greenpeace, captures the MP saying the independent anti-wind farm candidate, James Delingpole, had announced his candidacy as part of a "plan" to "cause some hassle" and drive the wind issue up the political agenda.

He is also filmed claiming he helped Delingpole by providing him with "a handful of people who will sort him out", including the deputy chairman of his own constituency party, who had stood down and then became the anti-wind candidate's campaign agent.

Delingpole, a Telegraph writer and climate change sceptic, withdrew from the race two weeks ago the day after the energy minister, John Hayes, gave a controversial interview to the Daily Mail in which he said the development of onshore wind farms in Britain should be reined in.

Asked by the Guardian whether his comments to the Daily Mail were timed to coincide with Delingpole withdrawing his candidacy, Hayes said: "James Delingpole was never a candidate in this byelection." He did not deny he had been communicating with Delingpole via Heaton-Harris.

Heaton-Harris also denied supporting Delingpole's candidacy, saying that, because Delingpole pulled out before submitting a deposit, he was not technically a candidate. He added: "James Delingpole was never a candidate in this byelection, there was no conspiracy or 'conspiring with an opposition candidate'."

Delingpole wrote an article on 17 September saying he was "standing as an independent candidate in the Corby byelection" and had been meeting prospective voters. The same article described how he had told prospective voters they should not vote Labour, Liberal Democrat or Conservative "whatever you do".

The evidence that their own campaign manager covertly supported a rival candidate in order to "write [the anti-wind agenda] into the DNA of the Tory party" will be intensely embarrassing to the party, already trailing in the seat vacated when Louise Mensch announced she was unable to reconcile the demands of her family life with being an MP.

Conservative MP Chris Heaton-Harris is secretly recorded following the announcement that James Delingpole was pulling out of the Corby byelection race Greenpeace

In a second statement Heaton -Harris said: "The quotes attributed to me range from factually correct statements to me bragging about things beyond my control, which has so often before been the failing of politicians. The implication that I choreographed any sort of 'secret plan' is simply not the case and I apologise if that is the impression given.

"It can hardly be said that my wanting to "put this on the agenda" is new. I have spent years fighting on-shore wind, getting over 100 MPs to sign a letter to the prime minister, securing debates and raising questions in Parliament and touring the country speaking to anti-wind groups.

"It is a subject I am passionate about and will continue to work on until communities across my constituency, Northamptonshire and the country have the protection they deserve."

The first secret film was recorded about a month ago when campaigning was under way for byelection. A Tory councillor in Sussex registered Delingpole's campaign website, in which he declared himself to be an "independent anti-wind farm candidate for the Corby and East Northamptonshire constituency". He had sought support of local constituents and even tweeted that he "kissed a baby" during a public rally.

He was campaigning against candidates from all three main parties, including the Tory Christine Emmett, whose campaign was being run by Heaton-Harris, MP for the nearby constituency of Daventry.

Against this backdrop, Heaton-Harris agreed to meet Greenpeace undercover film-maker, Chris Atkins, who approached him at the Tory conference pretending to be a representative of a fictional lobby group called Windefensible. "There's a bit of strategy behind what's going on," Heaton-Harris told him. "I'm running the Corby byelection for the Tories … And Delingpole, who is my constituent, and a very good friend [inaudible] put his head above the parapet, but won't put his deposit down … It's just part of the plan."

In another section that is difficult to hear, Heaton-Harris appears to say he "suggested to [Delingpole] that he did it. Which puts me in a very awkward [inaudible]. Please don't tell anybody ever. But he will not be putting his deposit down. He just did it because it's a long campaign, it's six weeks to cause some hassle and get, and get people talking."

Heaton-Harris also says: "Next week hopefully John Hayes, James Delingpole and I will have a meeting somewhere."

Hayes and Heaton-Harris said on Tuesday that a meeting with Delingpole never took place. Delingpole did not respond to a request for comment.

Hayes firmly denied any involvement in a plot to raise the profile of the anti-wind campaign: "My views on onshore wind energy are longstanding and well known and certainly not contrived as an 'elaborate plan' involving Chris Heaton-Harris, James Delingpole or anyone else."

The undercover film also captures Heaton-Harris saying: "James Delingpole can go and endorse the Ukip candidate, don't give a toss about that. Maybe we've just moved the agenda on."

He added: "I've managed to provide [Delingpole] with a handful of people who will sort him out. So my deputy chairman, political, resigned from my local party and is running his campaign as his agent. So it's all professionally done. The whole point of that is to actually just put it on the agenda."

Heaton-Harris was asked by the film-maker if the plan was to get the anti-wind farm campaign on the agenda."Exactly," he replied. "And it will go through way past the Corby byelection stuff. I'm trying to write it into the DNA of the Tory party."

The former deputy chairman of Heaton-Harris's constituency party, Trevor Sherman, had indeed resigned his post on 15 August. He remained a member of the Tory party and was described by Delingpole as "a superb election agent".

The Conservative councillor who set up Delingpole's campaign website was Donna Edmonds. She said she did not believe there was a conflict of interest because she "knew all along" that Delingpole would pull out.

Heaton-Harris is one of the Conservative party's most prominent opponents of wind turbines. Earlier this year, he persuaded 101 Tory MPs to sign a letter to the prime minister saying that subsidies to the industry should be "dramatically cut".

Greenpeace said Heaton-Harris was one of a number of Tory politicians they secretly filmed in an attempt to assess whether the government was rowing back on its commitments to combat climate change.

The campaign group shared its footage exclusively with the Guardian. Heaton-Harris gave further details about his knowledge of Delingpole's campaign during a second meeting with the undercover reporter, which took place three weeks after the first. That encounter was on 31 October, the day the Daily Mail and Telegraph carried front-page stories based on an interview with Hayes who had called for an end to the spread of wind farms, announcing, "Enough is enough."

It was a dramatic intervention that came on the same day as the deadline by which candidates in the Corby byelection needed to submit their £500 deposit. Delingpole had not done so, just as Heaton-Harris had predicted weeks earlier.

Informing the undercover reporter that Delingpole was "pulling out" of the election, Heaton-Harris said the timing was "contrived". "So you have the speech [by Hayes], two front pages," the undercover reporter said. "And then Delingpole stands down and that's all sort of saying, 'My work is done'?" "Yeah, there's been a bit of leverage that he's given me," Heaton-Harris said. "I've been working on this since the ministerial teams changed."

The MP reflected on how Hayes was now a minister "in a department that absolutely hates him", but still had the support of the cabinet. Hayes' remarks about wind farms had caused "quite a nice bust-up between the Lib Dems and us", the MP said.

Heaton-Harris predicted that after Hayes' anti-wind intervention Delingpole would announce his support for the Tories. "So tomorrow in the Daily Telegraph, Delingpole's writing a big piece about government going in the right direction," he said. "You know, nice piece for the boss to see. Why [Delingpole] has pulled out [of the byelection] and why these things are essential in what he's doing."

The undercover reporter asked: "Was Hayes sort of smiling on that whole adventure?" The MP replied: "Nothing in politics, even if it happens by accident, nothing happens by accident."

The next day Delingpole wrote in the Telegraph: "Have I just broken the record for the shortest and most successful election campaign in the history of politics?" Delingpole praised Hayes' remarks on wind farm policy. "And did my own brief involvement in the Corby byelection play its part in concentrating David Cameron's mind and shifting government policy? Well obviously I'd like to imagine so, but I'm not going to boast." Responding to the Greenpeace allegations, Heaton-Harris said he had "always hoped" that Delingpole would not formally stand in the constituency and insisted: "I would never betray a party I have been a member of for 25 years."

Heaton-Harris added that it was not uncommon or against party rules for political parties to have "open communication channels on a frequent basis" with rival factions during elections. He added he "would never dream of attempting to 'subvert the democratic process'."

John Sauven, Greenpeace executive director, claimed that their investigation revealed "how Britain's energy future is at risk of being hijacked by a militant faction of climate-sceptic and anti-wind MPs on the radical right of the parliamentary Conservative party".

"The Tories' campaign manager for this week's byelection is so opposed to clean energy that he appeared willing to betray his party and challenge the authority of the prime minister to promote his cause."

Hayes' row with his Lib Dem boss, Ed Davey, over renewables on Tuesday continued lastwhen he told Channel 4 News it was "end of story" for wind farms once the group of farms currently in the planning pipeline have been constructed.

The Department for Energy issued a statement saying that its policy was to have targets in the future for renewable energy and that no decision has been made on what proportion of that energy will come from different sources.