The pound has fallen sharply after the chancellor announced the biggest tax rises in a generation.

Over the last three days, sterling has dropped by 1.2% (in trade weighted terms) – the biggest fall in 18 months.

Between around 1.30pm and 5.30pm today, versus the dollar, it dropped from about 129.9c to the pound to about 128.6c. In the same period, against the euro, it went from 119.3c to the pound to about 118.4c.

In addition, yields for 10-year UK bonds – the cost or interest rate charged for long-term government borrowing – have gone past 4.5% for the first time in a year.

Ed Conway, Sky News’s economics and data editor, said those yields are “pretty much halfway towards the danger zone” – a zone identified by the Office for Budget Responsibility (OBR).

However, he said other European bonds had risen, too. “But the UK does seem to be moving faster than most of the others,” he added.

While cautioning that the budget is still very new, Conway said the “upshot” is that Rachel Reeves’s “room for manoeuvre” is already diminishing “because of market moves”.

Markets are reacting in “quite a violent way”, Conway said.

“It’s really unusual to see this after a budget, and that will have a bearing on how much this government will be able to afford in the future,” he added.

A sudden rise in the yields of 10-year UK bonds followed Liz Truss’s disastrous “mini-budget” of September 2022, which led to a surge in the cost of borrowing for ordinary consumers, while the pound slumped to a 37-year low against the dollar.

It is “certainly not like that at the moment”, Conway said.

Nonetheless, market movements will be “enough to really concern people at the Treasury”, he added, “because it suggests that a lot of traders are looking at how much money this government is borrowing, and they’re saying: ‘Hang on, maybe we’re going to charge you more’.”

While Conway said it does not feel like a “crisis point”, he said the “calculus for this government” may be changing.

Jack Meaning, UK chief economist at Barclays, said market reaction was “materially different” to what happened in 2022.

Bond yields since Ms Reeves’s budget are up by about 0.3%, while in 2022 the rise was about 1.5%, he said.

The conversation Barclays is having with its customers is also different to that in 2022, Mr Meaning added.

At that time, people were wondering whether a “big crisis point” had been reached.

This time, he said the focus is on comments from the OBR about a potential rise in inflation, and the potential knock-on effect as the Bank of England makes decisions on interest rates in the next few months.

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The prime minister’s official spokesperson refused to talk about bond prices.

“We don’t comment on market movements,” they said.

“The chancellor has been very clear that first and foremost, this budget has been about restoring fiscal stability, and she’s outlined two new robust fiscal rules, which put public finances on a sustainable path.”

Plans to ban smartphones in schools have been dropped after the government refused to support a change in the law, Sky News understands.

Josh MacAlister, the Labour MP for Whitehaven and Workington, put forward the proposal earlier this month to stop children “doom-scrolling” – the act of spending excessive amounts of time online consuming negative news or social media content.

However, upon revealing the details of his Safer Phones Bill, Number 10 immediately indicated it could not support the measure on the grounds that headteachers already have the power to ban phones – although it is not upheld in law.

It is understood Mr MacAlister has now dropped this element of his bill in the hope the government will support its other aspects.

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Mr MacAlister’s bill, which received broad support from cross-party MPs, education unions and charities, also calls for the age of “internet adulthood” – the minimum age to create social media profiles and email accounts – to be raised from 13 to 16.

It also wants to strengthen the powers of the regulator Ofcom to protect children from apps that are designed to be addictive and to commit the government to review further regulation if needed of the design, supply, marketing and use of mobile phones by children under 16.

Although the government indicated it could not back the phones ban, there has been some confusion on its overall position on the bill after some cabinet ministers, including Health Secretary Wes Streeting, signalled their support.

“Given the impact of smartphone use and addiction on the mental health of children and young people and the concerns from parents, this is a really timely debate,” he posted on X.

Speaking to Sky News earlier this month, Mr MacAlister, who chaired an independent review of children’s social care for the former government, said there was a “huge public health problem” with children around the world having increasing levels of mental health problems, issues with sleep and being impacted by phones in school.

“I’m only interested in one thing, which is making sure we can change the law to protect children and reduce screen time and get them back to having a healthier childhood,” he said.

“Parents are saying they’re facing an impossible choice between either keeping their kids off smartphones and ostracising them, or letting children get on these phones and seeing all the harmful effects that it can cause.

“And we need to shape some collective rules that help parents and teachers make better choices for children.

“Children themselves are recognising the harm that comes with all of the doom-scrolling.”

Current guidance to schools in England intended to stop the use of mobile phones during the school day is non-statutory, and was introduced earlier this year by the previous Tory government.

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Sky News has approached the government for comment. Earlier this month, a government spokesperson said: “We all want to find the best way of ensuring children are kept safe while also benefiting from the latest digital technology.

“The Online Safety Act will introduce strong safeguards for children, preventing them from accessing harmful and age-inappropriate content. This will include requiring companies to check the age of children so that parents can have peace of mind about the safety of their children online.

“The vast majority of schools already handle the use of mobile phones effectively, including with bans. Legislating for an outright ban would simply remove the autonomy from school leaders who know their pupils and their communities best.”

Mr MacAlister’s bill is due to have its second reading – the first opportunity MPs have to debate the contents of a bill – in March.