The UK's public sector is borrowing less money for government-funded projects, but the country's debt is growing.

The total amount the government is borrowing fell £6.1bn (€8.7bn, $9.4bn) to £25.1bn from April to June 2015 compared to the same time in 2014.

Despite this drop, new numbers released by the Office for National Statistics 21 July show that the government's debt is growing at the same time — indicating that spending has been on the rise.

At the end of June, the UK's debt sat at £1.5tr or 81.5% GDP. This was £77.4bn, or 5.4% more, than in June 2014.

The cost of paying interest on that amount is approximately £43bn. That's 8% of all the taxes the UK raises in a year.

In 2013 the UK's debt sat at 90.6% of GDP. In 2007 the UK's debt to GDP ratio was just 43.7%.

Growing debt numbers drew criticism from Chancellor George Osborne's opponents. "Under this Chancellor the national debt has soared and he has failed to build a more productive economy based on higher living standards and better wages," argued Chris Leslie MP, Labour's Shadow Chancellor.

"Today's update cannot hide George Osborne's broken promise on the deficit or the fact the national debt now stands at £1.51 trillion."

Leslie criticised the sale of national assets Royal Mail and the Royal Bank of Scotland, suggesting the government should focus on public spending that would "raise productivity".

The government's remaining 15% stake in Royal Mail was sold earlier this year at a discount. And a report at the end of 2014 said the government undervalued the firm in its first sell-off by £180m.

The sale of the government's 80% stake in RBS has raised eyebrows after £45.5 billion in taxpayer dollars bailed out the bank in 2008. The US government in early July also demanded the bank pay out $13bn to settle claims for bad mortgages it sold.

A report by the New Economics Foundation think-tank warns that the bank will need to be sold at a 15% discount to attract investors.

"As the OECD has warned," said Leslie, "'continued weak productivity' could lead to a higher deficit yet the Budget saw productivity revised down next year and for three years after that."