Chancellor George Osborne's hopes of slashing Government borrowing will be dealt a blow on Tuesday as the double-dip recession weighs heavily on the public finances.
Public sector net borrowing, excluding financial interventions such as bank bailouts, is expected to be between £16 billion and £16.5 billion, compared with £15 billion in May last year.
May is only two months into the financial year, but the weak figures will trouble the Chancellor who is aiming to trim total borrowing in 2012/2013 to £120 billion, excluding a one-off boost from the transfer of the Royal Mail pension fund into Treasury ownership.
May's borrowing figure will be impacted by a lack of tax receipts, which analysts said was a consequence of the recession and sluggish economic recovery.
Howard Archer, chief UK and European economist at IHS Global Insight, said: "May's public finances are expected to have been pressurised by the hit to tax revenues coming from weakened economic activity."
April's borrowing figures were flattered by a one-off £28 billion lift from the value of assets transferred from the Royal Mail pension plan.
But excluding this one-off impact, the Government actually recorded public sector net borrowing, excluding financial interventions such as bank bailouts, of £11.5 billion, £3 billion higher than City forecasts.
Earlier this month, George Osborne and the Governor of the Bank of England Sir Mervyn King unveiled a multibillion-pound lending scheme to stimulate economic growth - but ministers insisted the move was not a "plan B".