George Osborne only has a 50/50 chance of achieving his plans to post a surplus of £10 billion by 2020, according to the Institute of Fiscal Studies (IFS).
The director of the IFS Paul Johnson said the Chancellor will have to either raise taxes or introduce more spending cuts if economic growth is any worse than forecast by the Office for Budget Responsibility (OBR) for the Budget. On Wednesday, Mr Osborne revealed the OBR's latest forecasts were considerably lower than previous estimates, given that they were made just four months ago.
Speaking to the BBC, Mr Johnson said: “Within his very tight rule he will probably get away with this this time round. But there’s only about a 50-50 shot that he’s going to get there.
"“If things change again, if the OBR downgrades its forecasts again, I don’t think he will be able to get away with anything like this. I think he will be forced to put some proper tax increases in or possibly find yet further proper spending cuts.”
The OBR forecast growth of 2% in 2016, down from 2.4% estimated in November. Forecasts for 2017 and 2018 were reduced by 0.3 percentage points to 2.2% and 2.1%, respectively.
Mr Johnson added: “I think this is going to be the last chance he gets to move things around like this without doing anything genuinely big to the public finances.”