A report published today by spending watchdog Audit Scotland revealed the five-mile, six-lane stretch will now cost £692m, that's £35m more than the price last announced.

The project which is a partnership project between Transport Scotland, Glasgow City Council, South Lanarkshire Council and Renfrewshire Council is already three years late.

The new eight kilometres (five miles) stretch of road will continue the M74 motorway from Fullarton Road Junction, near Carmyle, to the M8 motorway west of the Kingston Bridge.

The orginal contract had only one bidder - a consortium including Balfour Beatty and Morgan Est and the original estimate in 2001 was £245m.

The study said poor management, inflation in the construction industry and delays caused by a failed legal challenge by environmental campaigners had caused costs to soar.

Transport Scotland said administration costs, buying land and the price of cable and pipe diversions - none of which were included in the original estimate - were also responsible.