Government borrowing rose unexpectedly last month, hampering efforts to shore up the public finances as the UK economy looks set to slow.
The Office for National Statistics said public sector net borrowing, excluding state-owned banks, increased by £2 billion to £6.9 billion in June compared with the same month last year.
Economists had pencilled in a total of £4.8 billion.
Prime Minister Theresa May has vowed to deliver a balanced budget by the ''middle of the next decade'', knocking back Chancellor Philip Hammond's previous target of putting the public finances back in the black by 2020.
Mr Hammond faces an increasingly tough challenge to drive down the deficit, as consumer spending is squeezed by high inflation and sluggish wage growth, threatening to drag on the Government's tax income.
The statistics agency said the budget deficit for the current financial year to date - April to June 2017 - climbed by £1.9 billion to £22.8 billion compared with the same period last year.
The Office for Budget Responsibility (OBR), Britain's fiscal referee, expects the Government to record a deficit of £58.3 billion for the financial year to March 2018.
Focusing on Britain's debt pile, public sector net debt excluding state-owned banks jumped by £128.5 billion to £1.75 trillion, equivalent to 87.4% of gross domestic product (GDP).
The latest update on the budget deficit comes just a week after the OBR flagged the potential threats to the public finances in its first Fiscal Risks report.
Putting the public finances through the same stress tests faced by banks, the watchdog said the Government's fiscal targets ''would be missed by a large margin''.
It added that the UK's debt was higher than before the banking crisis, meaning the UK's financial position was ''much more sensitive'' to higher inflation and interest rates.
Brexit had the potential to exacerbate potential financial shocks, the OBR said, while it also highlighted the risk of higher public spending if the Government responds to ''austerity fatigue''.
On productivity, it warned that if Brexit uncertainty shaved just 0.1 percentage points off growth over a 50-year period then the Treasury's coffers would take a £36 billion hit and the economy would be £97 billion worse off overall.
Responding to June's borrowing announcement, a Treasury spokesman said: "Today's release shows that our national debt, at £65,000 for every household, is still too high and leaves us vulnerable to any future shocks.
"That is why we have a credible fiscal plan to get debt falling and deliver the sound public finances needed for a stronger economy and higher living standards."
The ONS said Government spending rose by 8.3% to £59.9 billion in June compared with last year, while tax receipts lifted by 4.6% to £54.3 billion.
The Treasury saw VAT climb by £400 million to £11.4 billion over the period, as income tax takings also stepped up by £800 million to £12.7 billion.
However, corporation tax dropped by £200 million to £4.8 billion last month.
Samuel Tombs, chief UK economist for Pantheon Macroeconomics, said higher government spending was a key factor behind the last month's borrowing rise.
He said: "The jump in borrowing in June primarily reflects a £4.6 billion, or 8.3%, year-over-year leap in central government current expenditure.
"Although spending rose in most areas, a £1.2 billion increase in interest payments and £0.8 billion rise in contributions to the EU's budget, partly to correct for underpayments in previous years, were to blame for the particularly strong growth."
John Hawksworth, PwC's chief economist, said: "June saw a modest deterioration in public finances, with borrowing around £2 billion higher than a year earlier.
"This followed two months in which the deficit was almost identical to the year before.
"The general pattern is consistent with the OBR's March forecast that we might see some increase in the budget deficit this financial year, as the economy slows and some one-off favourable factors from last year unwind.
"Nonetheless, the deficit may still come in below the OBR's £58 billion forecast for 2017/18, given that the deficit in 2016/17 is now estimated to be £5.5 billion less than the OBR projected in March. So the increases in borrowing we are now seeing are from a lower base."
Labour's shadow chancellor John McDonnell said: "These figures reveal the continued failure of Philip Hammond and the Conservatives.
"Seven years of Tory cuts have left our economy weaker, with falling wages, yet the deficit has not been eliminated two years after they claimed it would be, and the national debt continues to rise.
"The Chancellor should stop handing out massive tax giveaways to big businesses and the super-rich, and instead give our hard-pressed public sector workers a pay rise, so we can end the travesty in our country of nurses having to rely on food banks.
"Only a Labour government will set out a serious plan for the public finances, with strategic investment underpinned by our fiscal credibility rule, to help build the high wage, high skill economy of the future for the many, not the few."