The cost of government borrowing has crept higher as Keir Starmer’s crucial speech failed to dispel investor “jitters” in the bond markets over political instability combined with fears of rising inflation. The yield, effectively the interest rate, on the benchmark 10-year UK government bonds (known as gilts) rose eight basis points (or 0.08 of a percentage point) to 5% on Monday. The yield on 30-year gilts rose 9.3 basis points to 5.67%, edging closer to the 28-year high of 5.78% last week when uncertainty about Starmer’s future as prime minister was intensifying. In his speech , Starmer said he would fight any leadership challenge and would not walk away from his responsibilities after Labour’s drubbing in local elections in England and parliamentary contests in Scotland and Wales last week. Borrowing costs fell on Friday as the results of the elections emerged with signs that Labour had not suffered as badly as first feared. Those falls, however, were more than erased by Monday’s rises.…