Building new nuclear power stations will make it harder for the UK to switch to renewable energy, said one of the top German officials leading the country's nuclear energy phase-out.

Germany said shortly after the Fukushima disaster in March that it would phase out its nuclear plants by 2022, while the UK is planning to build eight new nuclear plants as well as massively increase the amount of energy generated from wind power.

But Jochen Flasbarth, president of the Environmental Protection Agency in Germany, who advises the German government, said: "We are not missionaries, and every country will have to find its own way in energy policy, but it is obvious that nuclear plants are too inflexible and cannot sufficiently respond to variations in wind or solar generation, only gas [power stations] do."

Flasbarth robustly defended Germany's nuclear phase-out, saying it would be smoother than critics think. "The phase-out is doable and I don't expect unsolvable problems," he told the Guardian in an interview. "I wonder why Germany feels the pressure to defend its decision, but not the countries who stick to nuclear energy, which has been proved to be unsustainable."

He said he did not expect power shortages and it would not be necessary to import nuclear power from neighbouring countries such as the Czech Republic. "During the last month, there was no need for electricity imports due to capacity shortfalls in Germany. Short-term imports were merely market-driven," he said.

Nuclear power is deeply unpopular in Germany, with polls showing around 80% of Germans backing Angela Merkel's decision this year to phase out nuclear faster than planned.

A new poll published on Friday suggests that globally, just 22% of people agree that "nuclear power is relatively safe and an important source of electricity". However, the Globescan poll of 23,231 people in 23 countries showed that support in the UK actually rose from 33% to 37% since 2005. That chimes with a British Science Association-commissioned poll published in September showing UK support for nuclear power has remained steady since Fukushima. It found 41% of respondents agreed that the benefits of nuclear power outweighed the risks, up to 38% in 2010 from 32% in 2005.

Flasbarth also rebutted suggestions that Germany's nuclear phase-out could increase its greenhouse gas emissions, which it plans to cut 40% by 2020. Stephan Kohler, head of the German Energy Agency, has criticised the phase-out, saying that it contradicts the government's carbon-cutting efforts as more coal will be burned.

Although eight of Germany's 17 nuclear reactors have been shut down immediately and the remaining nine are to be taken offline by 2022, Flasbarth said greenhouse gas emissions will fall due to the European-wide emissions trading system. If companies burn more coal they need more emissions certificates – limiting certificates elsewhere. "There would only be a problem if energy suppliers lobby successfully against strict greenhouse gas limits after 2020, or for new subsidies for coal power plants," Flasbarth added.

Other critics of the nuclear phase-out, including Juergen Grossmann, head of energy giant RWE, have said companies would turn their backs on the country as energy prices would rise. Grossmann said: "The deindustralization won't come all at once. It will be a gradual process." Flasbarth said such fears were overblown.

Consumers will pay little for the new energy strategy, Flasbarth said. "We will have a slight increase during the next ten years in renewables while our energy infrastructure will be refurbished, but no expert has stated that prices rise more than 5%. The renewable track is economically the best one. The energy intensive industry is actually privileged, ie they pay lower energy taxes and get direct and indirect subsidies."

To fill the power gap after the nuclear phase-out, the new energy plan also includes fostering growth of green energies, moreso than any other industrialised nation. Wind turbines, biomass plants and solar panels, power storage sites and new grids are all planned.

Tennet, a private grid operator, warned in a letter to chancellor Merkel that they can not connect offshore wind turbines to the onshore grid as fast as hoped. "The warning letter to Merkel came from a company with a shortage of capital. This is a very specific situation with regard to this company, but we do not have a structural problem. We have to make big efforts, but there are enough companies ready for the task," Flasbarth said.

The German Energy Agency has calculated that 3,600km of high-voltage transmission lines will be needed by 2020. Public initiatives against "monster masts" have already been founded and have received broad media coverage. But the German public's opposition to some renewable energy developments is dwarfed by the opposition to nuclear. Thousands of demonstrators took the streets in cities across the country after Fukushima, and badges saying "Atomkraft nein danke" became popular. Flasbarth says this anger goes back to 1970 "when nuclear power was very much connected to nuclear weapons and East and Western Germany had the highest density of nuclear weapons". He added: "Those who argue that there will be a lack of public support for renewables are driven by wishful thinking."