The Chancellor's devolution revolution has been dealt a blow after Cambridge has rejected a three county deal and elected mayor set to be announced in next week's budget.

The city's council and the Cambridgeshire's business-lead local enterprise partnership said today that it could not support the current Norfolk, Suffolk and Cambridgeshire proposal which has been drawn up over the last fortnight.

But the Chancellor still wants to announce an 'Eastern powerhouse' when he delivers his spending blueprint next week, with other leaders believed to have agreed in principle to the deal.

Council leaders and local enterprise partnerships were offered £30m each year for the next 30 years in return for an elected mayor, although Mark Reeve, the boss of the GCGP local enterprise partnership said there was no clarity about whether transport projects which had already been promised, such as Ely junction, would need to be funded through the deal or if they would be delivered in addition to it.

While claiming it was keen for further discussions, Cambridge City Council said they had rejected proposals for a 'massive' 23 council combined authority, with a powerful new regional mayor, after the government had rejected its 'asks' on affordable housing.

They wanted funding and 'flexibilities' to allow the council to replace one for one all Cambridge council homes being lost under Right to Buy.

Leaders have been locked in days of talks over the last month trying to hammer out a deal in time for the budget after Lord Heseltine and communities secretary Greg Clark travelled to Cambridge last month to urge Cambridgeshire leaders to join forces with Cambridgeshire.

Lewis Herbert, leader of Cambridge City Council, said: 'Our focus is on what is best for Cambridge residents, businesses and workers, and our clear conclusions are that the government's rushed proposals to add Cambridgeshire councils to a Norfolk and Suffolk deal, which is nearly completed, are not the right deal for Cambridge, not the right deal for our world-leading economy, and not the right deal on retaining the affordable rent council housing that so many of our residents and their children desperately need.

'Given the potential risks to the thriving Cambridge economy particularly on housing supply, and the sweeping powers of the regional mayor across the three counties, we are really left with no other choice but to reject the current proposal and seek a better deal, particularly in the belief that other councils share many of our concerns and will probably agree with us when they see the final plans in a few months.'

Mr Reeve, who is chairman of the LEP, said: 'The proposed tri-county deal will not deliver what we need, and it is clear that our business representative organisations also cannot see how a devolution deal can work over the tri-county area.

'We have serious concerns about the amount of money being offered to the whole area in return for signing a devolution deal, not least as our economy is one of the country's major contributors to Government. A view that is supported by our local business community and business representative organisations, which include the Institute of Directors, FSB, CBI, and Chamber of Commerce.

'£30 million a year for 30 years to tackle the many infrastructure challenges we face is simply not enough. What's more, the funding is not indexed and part of it will be used to establish and run the mayoral office, further reducing the amount of money available to spend on vital projects'.

He added: 'Our concerns go beyond the money. We are not convinced that a Mayor across such a large geography will help economic growth across Greater Cambridge Greater Peterborough. Covering an area that in width is the equivalent of London to Bristol with a single Mayor just doesn't add up for us. We don't believe the business voice can add value in the proposed mayoral governance structure, where just two out of the 25 voices will represent business.'