Stopping climate change is probably more important than stopping Brexit, Liberal Democrat economic spokesman Sir Ed Davey has admitted.

Sir Ed said the Liberal Democrats have pledged to invest heavily in environmental policies as “stopping climate change is probably even more important than stopping Brexit”.

He added that a Liberal Democrat government would be “far more economically responsible” than any other party, partly due to the economic growth that will occur by staying in the EU.

The Liberal Democrats are expected to announce that they would spend £100 billion with a five-year investment that would “jump-start” efforts to combat the “climate emergency”.

Speaking on Radio 4’s Today Programme, Sir Ed said the £100 billion the Liberal Democrats are pledging to spend on climate change would be invested in “clean transport, clean energy, on insulating people’s homes and protecting the environment”.

“We’re doing this today because we believe that stopping climate change is probably even more important than stopping Brexit, it’s fundamental to what Liberal Democrats are talking about.”

He added: “With these policies we want to make Britain the world’s first climate-friendly economy.”

The UK’s economy will grow if the UK remains in the European Union, he added.

Questioned on the large amount of money being invested in the climate change policy, Sir Ed added: “Because we’re staying in the European Union our economy will grow, it will grow faster than proposals from either the Conservative and Labour Party, and because you’ve got extra growth, we believe our debt burden will fall.”

Sir Ed also claimed that a Liberal Democrat government would impose fiscal rules that are “tougher” than those proposed by both the Conservatives and the Labour Party.

He added that by staying in the EU, the Liberal Democrats will be “far more economically responsible” than any other party.

“We’re actually supporting a new fiscal rule today that the Resolution Foundation have proposed, and it’s basically using all of the government’s balance sheet, and saying as long as you’re improving the balance sheet, so your assets are growing faster than your liabilities, you’ve got sustainable approaches to managing debt and investment.

“So we’re actually going to have tough fiscal rules. Actually on current spending, our fiscal rules are going to be tougher than the Conservatives and the Labour Party.

“Why? Because we believe the next government has to be very economically responsible.

“And first of all by staying in the EU we’ll be economically responsible on growth, but on our fiscal rules, we’ll ensure that our overall spending package, whether it’s on current spending or capital spending, we’ll be far more responsible than either of the other parties.”