It plunged to a record low against the dollar last month, while borrowing costs went up sharply in the aftermath of the mini-budget. After the government promised huge tax cuts without saying how it would pay for them, investors were spooked.
Plans for spending and tax on 31 October are set to be announced on 31 October in his economic plan, which the Treasury confirmed was set to go ahead, although there are reports that it could be delayed due to the leadership race.
A fall in the value of the pound increases the cost of goods and services imported from overseas, because of the weakness of the pound against the dollar or euro, for example, it costs more for companies in the UK to buy things such as food, raw materials or parts from abroad.
Carl Emmerson, Deputy Director of the Institute for Fiscal Studies IFS, said government borrowing was almost as expected for the first half of the year, but warned that it was likely to rise much higher.
This month, the huge cost of government support for household and business energy use only began in earnest, so there is not a guide to how much borrowing will be over the whole of the financial year. We will do whatever is necessary to drive down debt in the medium term and make sure that taxpayers' money is well spent, putting the public finances on a sustainable path as we grow the economy.