A NEW £2.3bn Scottish bridge will only be built because of controversial spending rules that deprive much poorer Merseyside of similar cash bonanzas, the Government has admitted.

Troubled plans for the new Forth Crossing, on the edge of Edinburgh, were rescued by a funding boost from the much-criticised Barnett Formula, an inquiry was told.

Scottish Secretary Jim Murphy said there was a direct “read across” from the formula – which delivers much higher public spending in Scotland – to the Treasury grant allowing the road and rail bridge to be built.

The revelation is the starkest illustration yet of how the rules fund major projects north of the border that would almost certainly be blocked in the English regions, or be forced to find private finance.

In Merseyside, the Merseytram project collapsed in 2005, when then Transport Secretary Alistair Darling refused to hand over £170m previously pledged to Line One between Liverpool city centre and Kirkby. Although plans for a £431m second Mersey Crossing are progressing – after a decade of delay – only £86m is coming from the Government, with the rest to be raised through the Private Finance Initiative (PFI) and toll revenue.

In contrast, the Treasury has pledged £1bn in cash to help build the new Forth Crossing, half of which – it has now been revealed – will only be delivered because of the Barnett Formula.

Last night, its author, Labour peer Lord Barnett, attacked the discrepancy in funding, saying: “It’s quite clear to me that the formula was never intended to work in this way.”