Sir Keir Starmer is facing the threat of a House of Commons rebellion just a fortnight after becoming Prime Minister.
Left-wing Labour MPs are seeking to put pressure on Sir Keir over his stance on the Gaza crisis and the two-child benefits cap.
They have lodged their discontent with the PM's approach to both issues by tabling amendments to yesterday's King's Speech.
Around 15 Labour MPs are already backing a demand for the Government to suspend arms sales to Israel and 'immediately' recognise the state of Palestine.
And a similar number have declared their support for an amendment calling on Sir Keir to abolish the two-child benefits cap.
Both amendments to the King's Speech are set to be debated by MPs over the coming days, as the Commons scutinises the Government's legislative agenda.
Sir Keir Starmer is facing the threat of a House of Commons rebellion just a fortnight after becoming Prime Minister
Left-wing Labour MPs are seeking to put pressure on Sir Keir over his stance on the Gaza crisis and the two-child benefits cap
Labour backbenchers Zarah Sultana (left) and Kim Johnson have tabled amendments to the King's Speech
Zarah Sultana, the Labour MP for Coventry South, has tabled the amendment calling for Britain to suspend arms sales to Israel.
It is being supported by Labour ex-shadow ministers John McDonnell, Diane Abbott and Rebecca Long Bailey, as well as former party leader Jeremy Corbyn, who is now an independent MP.
It calls on the Government to 'support an immediate ceasefire in Gaza and release of all hostages' and 'to immediately recognise the state of Palestine'.
The amendment also demands Sir Keir 'restore funding for the United Nations Relief and Works Agency', 'drop the challenge to the International Criminal Court's jurisdiction in Gaza', and 'immediately suspend export licences for arms transfers to Israel'.
In an article for the Guardian, Ms Sultana said the Labour Government 'must do the right thing and stop enabling Israeli war crimes'.
'We must urgently pull every lever and strain every sinew to pressure the Israeli government to abide by international law and end this assault,' she wrote.
'This is not simply a moral duty, but a legal one too.'
She added: 'Up until now, I have been challenging a Conservative government for its complicity in crimes against the Palestinian people.
'That complicity must end now that we have a Labour government. So I urge colleagues: uphold international law, suspend arms sales to Israel, and back my amendment.'
Sir Keir has faced a series of rebellions by Labour MPs since the October 7 terror attacks on Israel last year.
The party also suffered a general election backlash in some areas over Sir Keir's stance on the Gaza crisis.
This included former shadow cabinet minister Jonathan Ashworth losing his Leicester South seat to a pro-Palestinian independent candidate.
Sir Keir has backed an immediate ceasefire in Gaza, while Labour's manifesto said the party was 'committed to recognising a Palestinian state'.
Prior to becoming PM, he suggested Labour would carry out a review of legal advice on UK arms sales to Israel if he won power.
Yet Sir Keir has frequently supported Israel's right to defend itself in the wake of the Hamas attacks.
Ms Sultana's amendment, which is already being backed by around 15 Labour MPs, calls for Britain to suspend arms sales to Israel
Ms Johnson's amendment to the King's Speech demands Sir Keir 'abolish the two-child cap on benefits'
Figures from the Department for Work and Pensions showed there were some 440,000 households affected by the two-child benefits cap
It was previously reported that Labour might delay recognising a Palestinian state so as not to draw a dividing line with America and other Western nations.
But, speaking at last week's NATO summit, Sir Keir suggested he could act before the US, saying: 'So far as our policy is concerned, I'll determine our policy, not follow anyone else.'
Kim Johnson, the Labour MP for Liverpool Riverside, has tabled an amendment to the King's Speech demanding Sir Keir 'abolish the two-child cap on benefits'.
Before becoming PM, Sir Keir said he would ditch the two-child limit 'in an ideal world' but added that 'we haven't got the resources to do it at the moment'.
He is under growing pressure from left-wing MPs, campaigners and charities to scrap the cap now that Labour are in power.
The two-child benefit cap, introduced by ex-chancellor George Osborne, prevents parents from claiming universal credit or child tax credit for a third or additional child born after April 2017.
With more than four million children now living in low-income households, the Government yesterday made an apparent bid to try and appease critics.
It committed to a ministerial taskforce to begin work on the child poverty strategy.
Mr McDonnell, the Labour former shadow chancellor, welcomed the move but also demanded Sir Keir 'produce a timetable' to scrap the benefits cap 'within weeks'.
He told MPs yesterday: 'There is a simple act and we all know it, there is one simple act that could lift 300,000 children out of poverty this month, and it would be the scrapping of the two-child limit.
'I was in this House when the Tories introduced it, it was introduced as part of the stigmatising of all those on benefits.
'I did a speech, I actually think I said I'd swim through vomit to vote against this piece of legislation, and some of the nauseous speeches from the Tories at the time almost meant I would have to.
'It was an appalling form of attack on the poorest within our communities. I think we just need to lift that stigma, lift that impact, but we need to do it quickly.
'So, yes, set up this taskforce by all means, but produce a timetable that within weeks we will scrap the two-child limit.'