With an iPad in one hand and a new workers’ contract in the other, John McDonnell believes that the Labour Party can build a better economy for Britain.

After a terrible week for the party, the Shadow Chancellor will outline his vision of how greater investment and employment security can create economic growth in a speech today at Imperial College’s Incubator for business startups.

He will commit a Labour government to ensuring that at least 3.5% of UK gross domestic product is spent on improving the country’s infrastructure.

And he will also criticise the Chancellor, George Osborne, for short-termism ahead of the government’s Spending Review next week. “Osborne may be trying to close the fiscal deficit. But by failing to invest, he is opening up a massive deficit with the future,” he will say.

“We believe that any fiscal rule should ensure government’s current spending is brought into sensible balance, consistent with sustainable economic growth, whilst allowing vital investment to continue.”

McDonnell will point out that Britain spends less as a share of GDP on research and development than France, Germany, China and the United States, all of whom are increasing their commitment to science and technology.

“The OECD thinks that, as a minimum, a developed country like Britain should be spending 3.5% of GDP on infrastructure. Labour in power will meet and better that commitment, reversing decades of underspend,” McDonnell will say.

“The Royal Society recommends a target of meeting at least the OECD average spend on research and development of 0.67% of GDP by 2020. A Labour Government will aim to exceed this, with total spending – from both public and private sources – of at least 3% of GDP by 2030.”

McDonnell will also promise that a Labour government would offer a “new contract for a new workforce”, extending existing employment protection to the self-employed and those on non-traditional contracts.

And he will also promise to invest in further education and look into changing the corporate tax system to incentivise companies to invest in new technology and skills training.

This week has been a bad one for Labour and the shadow chancellor, with Ken Livingstone’s comments about Kevan Jones’s mental health and the revelation that McDonnell had signed a statement from the Socialist Campaign for a Labour Victory advocating abolishing MI5, special police forces and armed officers.

He initially denied it but was then pictured in a photo published by the Sun holding the statement. His office insisted that he had not been aware of the full list of demands and supports additional funding for the security services to protect the public against terrorism.