Nigel Farage will this week outflank Sir Keir Starmer by committing to scrapping the two-child benefit cap and fully reinstating the winter fuel payment.

The Reform leader will appeal to Left-leaning voters in a challenge to Sir Keir in a speech launching his biggest attack yet on the Prime Minister.

His intervention is likely to spark a fresh wave of demands from Labour rebels for Downing Street to speed up planned policy shifts on both fronts.

Sir Keir is open to scrapping the two-child benefit cap but Rachel Reeves, the Chancellor, is understood to be resisting an immediate announcement until she can set out how it would be funded.

Removing the cap entirely, combined with reinstating winter fuel payments for some pensioners as announced last week, would cost the Treasury as much as £5 billion, making tax rises more likely.

No 10 is reportedly considering a plan to reinstate the payment to all pensioners then recoup it from the richest through their tax returns.

Mr Farage will use his first address since Reform’s local elections triumph to warn the Prime Minister that traditional Labour voters are turning to his party.

He is expected to say: “Starmer is one of the most unpatriotic prime ministers in our history and this past week has been evidence of that.

“The Prime Minister is out of touch with working people, he doesn’t understand what they want and how they feel about the big issues facing Britain.

“It’s going to be these very same working people that will vote Reform at the next election and kick Labour out of government.”

The Reform leader will commit to ending the two-child cap, which was introduced by the Conservatives in 2017 to cut the benefits bill.

A Reform source said: “We’re against the two-child cap and we’d go further on winter fuel by bringing the payment back for everyone.

“That’s already outflanking Labour.”

Zia Yusuf, Reform’s chairman, has said the party would pay for policies like the reinstatement of the winter fuel payment by cutting the foreign aid budget, closing asylum hotels and ending net zero subsidies.

The two child-benefit cap blocks parents from claiming Universal Credit or child tax credit for more than two children and has been blamed for driving a rise in poverty.

Mr Farage has previously spoken about how both the welfare and taxation systems should be used to encourage families to have more children.

Sir Keir is under growing pressure to abolish the two-child benefit cap to appease as many as 150 Labour rebels who are threatening to vote down separate cuts to disability benefits.

He backs ending the limit, but is said to be facing pushback from Morgan McSweeney, his chief of staff, and Ms Reeves, who are wary of the £3.5 billion cost.

The two-child benefit cap will now be either watered down or abolished, it is understood, but an announcement on the final course of action has been delayed until the autumn budget.

That will give the Chancellor enough time to work out how the change will be paid for, with a widespread expectation that she will have to raise taxes.

But the delay has angered some Labour MPs, who have demanded No 10 take action now.

Dame Meg Hillier, the Labour chairman of the Commons treasury committee, said lifting the cap was “the only way we’ll lift children out of poverty in this Parliament”.

Sir Keir placated some rebels earlier this week by announcing that he would perform a partial about-turn on the winter fuel allowance.

The Prime Minister said he would change the rules so that “more pensioners” would qualify after the policy was blamed for Labour’s local elections defeat.

But he will now come under pressure to match Mr Farage’s pledge to fully reinstate the payment to all pensioners, at a cost of about £1.4 billion a year.

Reform ‘on course to win next election’

In his speech, Mr Farage is set to launch a wide-ranging attack on Sir Keir covering immigration, the Chagos Islands deal and his EU reset.

He is expected to say: “Immigration is still at a historical high and Labour don’t have the want or political will to do what needs to be done to bring it down to net zero, which is what the majority of the British public want.”

He will be flanked by Reform’s new council leaders, mayors and its latest MP, Sarah Pochin, who won her Runcorn seat in a by-election victory over Labour.

The speech is designed to send a message that the party is on course to win the next election and that backing it is not a wasted vote.

Mr Farage’s previous parties, the UK Independence Party and the Brexit Party, failed to make the transition from protest votes to frontrunners in general elections.

Reform officials are confident that the local elections, when the party took control of 10 councils, represented a “coming of age moment” where voters viewed it as a realistic party of government.

The party has led in the national opinion polls since the middle of April and was seven points ahead of Labour in the most recent YouGov survey.

Sir Keir has been seen to be tacking to the Right, particularly on immigration, to try to see off Reform’s threat, with Ms Pochin saying that Labour was “sounding more like Reform than Reform are”.