Jeremy Corbyn has accused the Labour government of “appeasing” Reform UK by “scapegoating” migrants and minorities for its own domestic policy failures, saying his new leftwing political party would take on Nigel Farage instead.

The veteran leftwing MP, who confirmed last week he was launching a new, as yet unnamed, movement with former Labour MP Zarah Sultana, said British politics was at a “critical juncture” with the rise of rightwing populism. He said he saw their role as providing hope, not fear.

And he accused the Labour party, which he led between 2015 and 2020, of “paving the path” for Reform’s electoral success, by failing to take on a “rigged economic system” and blaming immigrants for the problems in society.

In less than a week, more than 500,000 people have signed up to the new movement which is explicitly aimed at left-leaning voters who have backed Labour, the Greens or the collection of Gaza-focused independents who saw off Labour candidates in four constituencies in last year’s election.

Polling before the party launched suggested it could gather as much as 10% of the vote nationally. However, new parties usually struggle to maintain momentum, and turning polls into votes relies on building an effective campaign machine, which is difficult to do from scratch.

Writing for the Guardian, Corbyn said there was a “huge appetite” for a reset of the “broken” political system, under which the traditional two-party domination has broken down.

“Up and down the country, there is huge appetite for an economic reset. One that brings water, energy, rail and mail into public ownership. One that invests in welfare, not warfare. One that makes the wealthiest in society pay a bit more in tax to ensure that everyone can live in dignity,” he said.

“This is the political vision that can inspire hope, not fear. The great dividers want you to think that migrants and minorities are responsible for the problems in our society. They’re not.

“Those problems are caused by a rigged economic system that protects the interests of billionaires and corporations. By scapegoating migrants and minorities for its own domestic failures, Labour has paved the path for Reform UK.

“This Labour government is here to appease Reform. We are here to defeat Reform. We are at a critical juncture, and we need an alternative, now.”

The former Labour leader added: “Politics should be about empowerment. Instead, people are shut out of the decisions that affect their daily lives. For too long, top-down political parties have patronised their members and disempowered the communities they claim to represent.”