LONDON — Britain’s main opposition Labour Party announced Friday that if it wins a December general election, its new government will provide free, super-fast broadband across the entire United Kingdom.

It was the latest eye-catching offer in a campaign that suggests the main parties are keen to turn the spending taps back on after years of austerity under the ruling Conservatives.

“Not just any broadband, but the very fastest,” Labour Party leader Jeremy Corbyn promised. “Full-fiber broadband to every home, in every part of our country, for free.”

He was referring to the kind of high-speed connection that allows a high-definition movie to be downloaded in less than a minute.

That should appeal to British households that pay on average $38 a month for good but not great Internet — as well as the 7 percent of British households with no Internet.

Corbyn pitched his plan as one that will make Britain more fair and more competitive, asserting that only 10 percent of the country has access to full-fiber broadband, compared with 98 percent in South Korea.

Corbyn added: “And once it’s up and running, instead of you forking out for your monthly bill, we’ll tax the giant corporations fairly — the Facebooks and the Googles — to cover the running costs.”

He also said the transformation would take 10 years.

Labour’s gambit was immediately criticized by for-profit Internet providers — and Labour’s rivals in the Conservative Party — as needless, cumbersome and prohibitively expensive.

Conservative Prime Minister Boris Johnson called it “some crackpot scheme that would involve many, many billions of taxpayers’ money nationalizing a British business.”

But whereas in the 2017 general election, the Conservatives blasted Labour’s promises saying that there was no “magic money tree,” both parties now seem to have found it.

With a month of campaigning to go before the Dec. 12 elections, the dueling parties appear to be trying to woo voters with big-ticket holiday gift items.

Johnson is not only promising to “get Brexit done” but to support Britain’s “left-behind” towns, especially in the north and Midlands, where his party hopes to snatch up disgruntled Labour voters.

His Conservatives have vowed more spending on public services and infrastructure projects. They say they will pour money into the National Health Service, improve roads and bus services, and put 20,000 extra police officers on the streets. (Labour points out that since the Conservatives came into power in 2010, the number of police officers has dropped by more than 20,000.)

The Conservatives also say they will cut taxes for smaller pubs and mom-and-pop shops.

Labour, meanwhile, is promising nothing short of a self-described “radical transformation” of the British economy, with plans not only to provide “the gold standard” of broadband” but to take over Britain’s for-profit railways, postal service, water companies and energy providers. Labour is also vowing to usher in its version of a Green New Deal, which would accelerate renewable energy and phase out fossil fuels.

Many of Labour’s policies are popular with the public, but the party is still lagging behind the Conservatives. Pollsters say voters are more likely to trust Johnson than Corbyn with the economy, and Johnson’s personal ratings exceed those of Corbyn.

Nigel Farage, the leader of the Brexit Party, also gave a boost to the Conservative Party with his decision not to field candidates in seats that the Conservatives won in 2017.

But, of course, anything can happen over the course of an election campaign.

The Conservatives got off to a shaky start, with Jacob Rees-Mogg, the leader of the House of Commons, widely criticized for comments denigrating the victims of a massive fire at Grenfell Tower.

Johnson was also heckled by residents in flood-hit areas when he toured northern England this week.

Both parties are hoping their spending proposals will look attractive in that part of the country.

To provide free broadband, a Labour government would nationalize a division of for-profit phone and Internet provider BT, formerly British Telecom, the largest player in the sector.

In its calculations, Labour estimates it would cost $25 billion to nationalize and build out the broadband system, plus another $300 million annually to run it.

For-profit providers countered that Labour’s plan would not cost $25 billion but $100 billion.

In addition to nationalizing the broadband division of BT, called Openreach, another Labour official said it was possible that a Labour government might take control of the smaller players, including Virgin Media, Sky and TalkTalk.

On news of Labour’s plans, shares of BT fell 4 percent. But the stock quickly rebounded — in part because analysts concluded the takeover would never happen.