Leaders of the Civil Engineering Contractors Association have written to MPs in a bid to protect investment in key projects like Crossrail.

An emergency budget will be held before July 1 when new chancellor George Osborne will outline the extent of public spending cuts in a bid to bring down the country’s £163bn debt pile.

CECA has been in touch with key MPs and will extend its campaign this week to everyone in the Commons.

CECA is calling for clarity on the outlook for public spending to 2014 and a commitment to projects like Crossrail and the managed motorway programme.

Britain’s builders echoed the call for balanced and sustained investment. Chris Blythe, chief executive of the Chartered Institution of Builders, said: “We are entering unchartered waters and only time will tell if it is a success.

“What is clear is that if we are to go back to a pattern of consistent economic growth, there needs to be a sustained programme of national investment,” he said.

“Investment in the built environment can spread the benefits of an economic stimulus to all parts of the UK.

Blythe added: “For every £1 spent on construction output, £2.84 is generated in total economic activity, and 92p of every £1 spent on construction is retained in the UK.

The CIOB believes there is a golden opportunity to develop the low carbon skills that the industry needs to meet the green agenda.

“Unlike the debates, this government’s success will be measured by its ability to turn the words into substance,” said Blythe.

On the housing side Stewart Baseley, executive chairman of Home Builders Federation, said the time had come for the Conservatives to demonstrate there was substance behind their commitment to building more homes.

Warning that the national housing shortfall is now approaching one million homes, he said: “Reducing the regulatory costs imposed on housing developments, which have risen dramatically over the past ten years, must also be an immediate priority to make more potential sites viable.”

The house builders warned that introducing VAT on new homes, a pre-election proposal by the Lib Dems, would penalise first time buyers and result in fewer homes being built.

Mike Leonard, director of the Masonry Alliance, said: “It is good for the country that we have made the decision and we can get on with dealing with the worst financial situation in living memory.

“We hope the coalition will recognise the fundamental role of housing and construction in building a fare and just society.”

Leonard said the time had come for the industry to puts its full weight behind the Get Britain Building Campaign.

“We need to invest in social housing, cause the banks to lend and cut VAT to 5% on home improvements to help green our existing housing stock.”

He added: “This will provide much needed housing and jobs. And just as important, it will stimulate wealth creation through our manufacturing businesses, which was missing from all of the political manifestos.”