Patrick Harvie has been urged to pursue an alternative strategy to clean up heating systems amid claims heat pumps are not a realistic solution.

The Greens Zero Carbon Buildings Minister hopes to decarbonise one million homes by 2030 as part of the Scottish Government’s net zero strategy.

The Herald on Sunday revealed that Mr Harvie’s shake-up of energy efficiency ratings will see fossil fuel gas boilers penalised in a move to encourage more people to switch to sustainable heating systems.

Read more: Gas boilers set to be penalised under energy efficiency overhaul

But entrepreneur and Labour peer, Lord Haughey, has called on the Scottish Government to encourage people to install electric boilers instead of air source heat pumps, claiming the devices are flawed and could leave Scots out of pocket.

The businessman has accused Patrick Harvie of misleading Scots by encouraging them to buy air source heat pumps, claiming that “in most situations in Scotland” they do not work.

The Scottish Government has made thousands of pounds available in grants to help people switch to a heat pump.

In December, the Scottish Government moved to make it simpler and more affordable for people to install heat pumps with a standalone grant of £7,500 from the Home Energy Scotland scheme made available as well as an extra £1,500 to homeowners in rural areas.

A survey commissioned by WWF Scotland revealed that more than half of Scots would install a heat pump with some or no government support, while 40% would do so within the next five years.

Read more: Half of Scots support Harvie's plan to phase out fossil fuel boilers

Speaking to The Herald, Lord Haughey said: “I’m not impressed with them, with people like Patrick Harvie, telling the public they are an efficient vehicle to decarbonisation. It’s complete nonsense.

“They were never designed for that – they were designed to be air conditioning units.”

Lord Haughey criticised Mr Harvie for claiming “that heat pumps are carbon zero”, adding that they are “run on electricity”.

The peer has insisted that air source heat pumps do not work effectively and accused Mr Harvie of “putting a financial burden onto people”.

He said: “You will get situations where they do work, but in most situations in Scotland, they do not.

“If you take 2.9 million people in Scotland having to move to a heat pump, they are just going to accrue thousands in debt.

“I totally agree that we don’t want to be at the behest of Russia and want security over utility.

"If we all want security in relation to our utility, we have to move away from gas.

Read more: Heat pumps will cut energy bills amid fears over climate target

“But we should be moving to an electric boiler, which is much more cheaper and much easier to run than an air source heat pump.

“Why is it not a good idea to move from gas boilers to an electric boiler?”

Lord Haughey pointed to his development of 365 homes in the Gorbals and the prospect of installing heat pumps in the properties.

He said: “It only takes one of the residents to complain to Sepa over the noise and they will have to be switched off.

“This is not an attempt by me to get something cheaper, quite the opposite.

“But I think we should be spending that £9,000 or £10,000 on extra insulation and double glazing.

“Patrick Harvie is absolutely not being honest to the public.”

The peer claimed that the SNP-Greens administration is chasing heat pumps as the solution “because the English government gave them money for it”.

He added: “We are leading because we can get more money towards it.

“This is definitely not the best for the people of Scotland.”

Asked whether there was time for a rethink by the Scottish Government, Lord Haughey insisted it was “absolutely not too late”.

He said: “There are very few heat pumps being fitted.”

Earlier, Mr Harvie said although Scotland’s net zero aim is to decarbonize by 2045, “we’re starting now and we need to accelerate”.

He added: “So this is not far-off futuristic technology, heat pumps are a very well tried and tested technology.”

Mr Harvie said companies are investing in smaller, more efficient heat pumps, adding: “That’s where the innovation is going. That’s where the industry is going.

“And I genuinely hope that Willie Haughey chooses to invest a bit in R&D and catch up.”