George Osborne should change debt target, says IFS The first was to eliminate the structural deficit on a rolling five-year basis, and the second was to have national debt falling as a proportion of GDP by the 2015-16 financial year. Weak growth, which has knocked borrowing off-track this year as the deficit is currently running about 25pc above target, is making the second rule "problematic," Mr Emmerson said. He added that while the first rule "has much to commend it... the same is not true of the debt target." "Forcing debt to fall between two fixed dates does not ensure long-run sustainability, since it does not constrain the Government from allowing debt to rise inappropriately before or after those dates," he said. However, he said some kind of supplementary target was needed because the first rule "on its own does not limit the liabilities the Government accumulates." "Getting such a target right, and the timescale in which it should be achieved, is more important than having it in place straight away," Mr Emmerson stressed. It might also be possible to get a broad political consensus over these issues. Treasury officials are believed to be working on plans for a new supplementary target, but no decision has been made to replace the current debt rule in the autumn statement. One possibility would be to revive a version of Gordon Brown's "sustainable investment rule" - that net debt should not rise above 40pc of GDP. The Office for Budget Responsibility's (OBR) latest forecasts are for debt to peak at 76.3pc in 2014-15. The Chancellor will not receive the OBR's judgment on whether the target will be hit until a few weeks before the statement, due on December 5.