The government is expected to give the green light to the completion of the dualling of the A11 in its big announcement today on public spending.

Sources close to the heart of the coalition confidently told the EDP last night that chancellor George Osborne has decided to authorise the widening of the nine-mile single-carriageway 'missing link' in the Elveden area on the main Norwich/London highway.

He has been persuaded to make this an exception to the expenditure cuts because 'the economic case stacks up'.

Roads minister Mike Penning told the Commons in July that dualling the section of the road between Thetford and Barton Mills had a 'very, very high' benefit to cost ratio of 20. And the logic of that seems to have trumped even the government's determination to push through the most sweeping public spending cuts this side of the second world war.

The implementation of the �134m scheme would be the realisation of a decades-long dream to secure a first-class road link between Norwich and the national capital. The EDP has been campaigning for full dualling of the A11 since 1984.

Businesses, councils and MPs have joined together to make the case for full dualling, with the lobbying campaign ratcheted up in recent weeks as fears emerged that the scheme might not survive the cuts.

The fate of the scheme has been up in the air since a public inquiry was held into plans, with the publication of the inspector's report delayed until after the spending review.

Supporters have long argued that dualling would bring benefits totalling more than �500m to the regional economy, and earlier this year a delegation of coalition MPs lobbied treasury chief secretary Danny Alexander about the need to support the scheme, which is seen as a critical investment to helping the regional economy ride out the downturn. On Monday Norfolk MPs met at Westminster to restate their support for the scheme and urge ministers to use some of the �650bn they still had to spend to pay for the road.

Mr Osborne has come under sustained pressure to give the thumbs-up for the A11 from a united front of local MPs in the coalition parties.

West Suffolk MP Matt Hancock is a former top aide to the chancellor, and pushed the 20 benefit/cost figure into the public domain. 'Consultants working for the Highways Agency estimate that for that �134m cost the project will generate over �19m in indirect taxes, and economic benefits of over �550m for consumers, and �1.1bn for businesses. So on the government's own figures, benefits are over 20 times the cost. That is an astonishing figure,' he emphasised in the Commons three months ago.

In immediately confirming the benefit/cost ratio, Mr Penning signalled that the A11 campaigners were knocking on an open door. He also spoke of the personal knowledge he had of the road through taking his daughters to Center Parcs, and said he had experience of 'taking lives in one's hands' by trying to turn on to the A11 in Elveden.

Pressure on the government has also been exerted by Keith Simpson, an aide to foreign secretary William Hague, and Norman Lamb, aide to deputy prime minister Nick Clegg. A11 dualling has had friends in very high places in the negotiations about which schemes would survive the chancellor's axe.

Norwich South MP Simon Wright said: 'This has been the number one priority for us as MPs, and the business community and the EDP has been pushing for this. It's a very important issue for Norfolk, but we don't want to count our chickens just yet and we will just have to wait and see what the government and the department for transport says.'

South West Norfolk MP Elizabeth Truss said she believed the case for the road had been well made, and urged ministers to give it the green light. 'It's very much fingers crossed, but there's a very strong economic case for this on the chancellor's own criteria, which is why it's absolutely right they should do it,' she said.

Yarmouth MP Brandon Lewis said the A11 lobbying showed 'the coalition in action locally' and the road scheme had 'ticked all the boxes economically and politically'.

held into plans, with the publication of the inspector's report delayed until after the spending review.

Supporters have long argued that dualling would bring benefits totalling more than �500m to the regional economy and earlier this year a delegation of coalition MPs lobbied treasury chief secretary Danny Alexander about the need to support the scheme which is seen as a critical investment to helping the regional economy ride out the downturn.

On Monday Norfolk MPs met at Westminster to restate their support for the scheme and urge ministers to use some of the �650bn it still had to spend to pay for the road.

Mr Osborne has come under sustained pressure to give the thumbs-up for the A11 from a united front of local MPs in the coalition parties.

West Suffolk MP Matt Hancock is a former top aide to the chancellor, and pushed the 20 benefit/cost figure into the public domain. 'Consultants working for the Highways Agency estimate that for that �134m cost the project will generate over �19m in indirect taxes, and economic benefits of over �550m for consumers, and �1.1bn for businesses. So on the government's own figures, benefits are over 20 times the cost. That is an astonishing figure', he emphasised in the Commons three months ago.

In immediately confirming the benefit/cost ratio, Mr Penning signalled that the A11 campaigners were knocking on an open door. He also spoke of the personal knowledge he had of the road through taking his daughters to Center Parcs, and said he had experience of 'taking lives in one's hands' by trying to turn on to the A11 in Elveden.

Pressure on the government has also been exerted by Keith Simpson, an aide to foreign secretary William Hague and Norman Lamb, aide to deputy prime minister Nick Clegg. A11 dualling has had friends in very high places in the negotiations about which schemes would survive the chancellor's axe.

Norwich South MP Simon Wright said: 'This has been the number one priority for us as MPs, and the business community and the EDP has been pushing for this. It's a very important issue for Norfolk, but we don't want to count our chickens just yet and we will just have to wait and see what the government and the department for transport says.'

South West Norfolk MP Elizabeth Truss said she believed the case for the road had been well made, and urged ministers to give it the green light. 'It's very much fingers crossed, but there's a very strong economic case for this on the chancellor's own criteria, which is why it's absolutely right they should do it,' she said.

Yarmouth MP Brandon Lewis said the A11 lobbying showed 'the coalition in action locally' and the road scheme had 'ticked all the boxes economically and politically'.