A quick look at the actual evidence reveals that only two Labour governments have ever left office leaving the national debt higher than it was when they came to power, all of the others have lowered the national debt as a percentage of GDP.
On the two occasions that Labour oversaw increases in the national debt there were the mitigating circumstances of huge global financial crises. The Ramsay MacDonald government of 1929-31 coincided with the Wall Street Crash (they left a 12% increase in the debt to GDP ratio), and the Blair-Brown government of 1997-2010 coincided with
the 2008 financial sector insolvency crisis (an 11% increase). The other Labour governments all reduced the scale of the national debt,
Clement Attlee's 1945-51 government reduced the national debt by 40% of GDP despite having to rebuild the UK economy from the ruins of the Second World War. Harold Wilson's 1964-70 government reduced the national debt by 27% of GDP and even the Wilson-Callaghan government of 1974-79 managed to reduce the debt by 4% of GDP.
The majority of Labour governments have ended up reducing the national debt, and the two that didn't coincided with the biggest global financial crisis of the 20th Century and the biggest global financial crisis so far in the 21st Century.
In order to put this "
cleaning up Labour's mess" narrative to the test, it is useful to look at George Osborne's own record as Chancellor of the Exchequer.
In his first 3 years as Chancellor George Osborne managed to add more to the national debt than the supposedly "profligate and irresponsible" Labour party did in the 13 preceding years. In fact, in just 4 years George Osborne has increased the national debt in real terms more than every Labour party chancellor in history combined!
By George Osborne's own estimates, the national debt will have grown by 26% of GDP between 2010 and 2015. In the last 200 years of economic history there have only been three periods of debt accumulation worse than George Osborne's tenure as Chancellor of the Exchequer: