The EU has morphed into a force for "social injustice" as Brussels turns it back on "economic common sense" in pursuit of a political project, Iain Duncan Smith has claimed.The former work and pensions secretary issued the warning on 10 May as he argued that breaking away from the 28-nation bloc could help the worse off in the UK.

"No matter what those who want to remain say about the EU as a market place, the reality is that it is first and foremost a political project, the aim of which is the creation of an overarching federal power, above the nation states," the Conservative MP said.

"It is the reason why economic common sense cannot prevail and why many Greeks are now living in third-world conditions, Italian banks are becoming insolvent and terrible levels of youth unemployment have become, for the EU, a terrible price worth paying.

"Yet outside of the EU an independent Britain can design migration, agricultural, environmental, budgetary and trade policies that the rest of Europe seems sadly incapable of agreeing upon."

Duncan Smith, who dramatically resigned form David Cameron's government in March over proposed disability cuts, also branded Labour's pro-EU position as "ironic".

"Even [Lord] Stuart Rose of the Stronger In campaign has admitted that immigration cuts the pay of the poor in a rare moment of candour – and acknowledged that wages will go up for many Britons if immigration is restricted," the Vote Leave spokesman added.

"The downward pressure on wages is a trend will only get worse if we continue to have open borders with the EU – and would get most difficult in a recession."

Duncan Smith's speech comes as the EU referendum ramps up with just over a month to go before the 23 June vote. Boris Johnson and David Cameron went head-to-head with rival EU speeches on 9 May and Duncan Smith's coincided with the launch of Labour's pro-EU battle bus, where Alan Johnson branded Brexit campaigners as "extremists".

"They cannot find anything good to say and I think that's extreme," the Labour In for Britain chief told reporters. "We can all find things that are wrong with the EU, but they cannot find anything that's right – and that suggests a certain mentality that is not rational and is not balanced. The majority of British people have a rational balance, [and a] moderate approach to this question."

Alan Johnson and Jeremy Corbyn launch Labour's pro-EU battle busIBTimes UK