Ed Miliband is bringing the former deputy prime minister, John Prescott, back into frontline politics only months before May’s general election.

In a controversial move, the Labour leader has appointed Lord Prescott as his personal adviser with specific responsibility for climate change. His remit, according to aides, is to “bash heads together”.

The eye-catching development comes as an Opinium/Observer poll shows that the Conservatives have edged ahead of Labour for the first time in three years, apparently confirming a trend seen in other polls in recent weeks.

Writing in the Observer, Miliband says that he has appointed Prescott to help him as prime minister to force a more ambitious agenda on the world over carbon emissions at the global summit in Paris later this year. Linking climate change to the floods in Britain last year, Miliband writes of a potential deal at the talks: “I do not want to see Britain or any country having to adopt crisis measures to halt the slide into global catastrophe because we missed this critical opportunity now. A strong coalition for a weak deal will fail us all.”

However, the surprise appointment will inevitably be seen as a way to shore up Labour’s traditional working-class vote and address growing concerns that Miliband and the shadow cabinet are failing to cut through to the electorate.

Ukip is targeting disillusioned Labour voters in a number of north of England constituencies, where the party’s leader, Nigel Farage, has claimed it can replace the Tories as the main opposition and even steal some seats from Labour.

The Tories are up two points from last week on 35%. Labour now stands at 33%, down two points. The Liberal Democrats are on 6%, Ukip 15% and the Greens 7%.

Sources close to Miliband dismissed the significance of the latest survey, pointing out that Labour has been ahead in 20 of the last 25 polls. The latest figures would also still give Labour a slim overall majority, but they represent a steep drop in Labour’s polling numbers since the end of 2012 when it was ahead by 11 points. Adam Drummond, research manager at Opinium, said that the decline in Labour’s performance reflected the fact that fewer voters were now dissatisfied with the coalition’s economic performance.

He said: “Our data shows that not only do the Tories now have a slim lead but that David Cameron and George Osborne have a big lead on who is trusted with the economy and that more voters are now feeling the recovery.

“The proportion of people who say the economy is bad and that the coalition are to blame has declined from 28% back in 2012 to 16% now. More importantly, the proportion saying the economy is good and crediting the coalition for this has risen from 2% in 2012 to 19% now.”

The shopping magnate and labour donor, John Mills, said Labour should not “be too depressed by one or two polls” but admitted the party needed to get business onside.

He said: “I think the reality is that Labour has to get in with the business community. If it is going to be successful it has to make sure it carries business with it. And I think it will.”

Prescott, who turns 77 in May, resigned as deputy prime minister in 2007 as Tony Blair left Downing Street, and retired as an MP in 2010. His time in government was littered with controversies, including one occasion when he punched a protester during an election campaign and the revelation of a two-year affair with his secretary.

In 2012 he stood as the Labour candidate in the election to be the first police and crime commissioner for Humberside police, but lost to Conservative Matthew Grove.

He has previously used his Sunday Mirror column to criticise Miliband for giving up on winning an overall majority and for posing with a copy of the Sun.

Sources close to Prescott insist that he has intervened only in the interests of the party and that in speaking out he triggered an improved performance by the Labour leader.

Prescott still has a strong personal following and considerable experience in the field of climate change. He was the lead EU negotiator during the brokering of the Kyoto protocol in 1997, the first global deal to reduce carbon emissions.

Miliband, a former energy and climate change secretary, wants the Paris talks to set a goal of net zero global carbon emissions for the second half of this century.

He writes: “As the Intergovernmental Panel on Climate Change has said, if the world is going to hold warming below 2C, global emissions need to peak not long after 2020 and then decline rapidly to reach net zero in the second half of this century.

“The weaker the action now, the more rapid and costly the reductions will need to be later. To support me in this task I have asked John Prescott to advise me on how we can achieve the best deal at the summit in Paris.

“His abilities and experience, as one of the architects of the Kyoto protocol in 1997, must be used at this critical time for our future and there is no one better than John at bashing heads together to get a deal.”

Announcing his acceptance of the position, Prescott said: “My brief is to raise ambition on this crucial issue and I am proud to help the man I hope will be the next prime minister so that together we can help the next generation.”

Talks at the UN climate change conference in Copenhagen in 2009 failed because agreement between the developing countries and the world’s biggest polluters such as China and US could not be found.